I'm guessing you don't have a collection of things packed away that you could pull out and try on those shelves?

Lately I have been drawn to Murano glass pieces that are showing up at second hand stores. They are also available for not a lot of money on eBay.

Here is a link that might be useful: Murano glass on eBay

I'm a bit traditional too and I would use mostly books with nice book ends, maybe a small statue or three.

Books, of course! Also some attractive personal photos, or this beautiful vase from grayswings link would look great, along with some other similar items.

Here is a link that might be useful: vase

Is this your living room (therefore a bit formal) or your family room (therefore a bit informal)? Because if this is the family room, I see those shelves as the perfect place for all the DVDs and CDs and video games. Then I'd fill in the rest of the space with books and a few favorite objects. If those are adjustable shelves, I'd see if I couldn't get a couple more, to make better use of the space when shelving DVDs and CDs.

If this is in the living room and you want a more formal look, I'd go with lots of books, interspersed with a few attractive objects.

I have lots of books from FIL so they filled the library and then some.

If it were mine, I'd probably paint it white to match the fireplace so the whole space would feel more cohesive. What will you place your tv on, or under the tv? If you paint everything, whatever you place there will look more like it's all one unit.
Here's a white one with mostly books. And some others that have a nice mix of decorative items with some books and pictures. Notice how there aren't too many small things. Fewer, larger things will look better, I think.

[Traditional Family Room design[(https://www.houzz.com/photos/traditional-family-room-ideas-phbr1-bp~t_720~s_2107) by San Francisco General Contractor Podesta Construction

[Traditional Living Room design[(https://www.houzz.com/photos/traditional-living-room-ideas-phbr1-bp~t_718~s_2107) by Charleston Interior Designer LORRAINE G VALE, Allied ASID
If you don't paint it, then I'd consider making the wall behind it dark to make it more cohesive

[Traditional Media Room design[(https://www.houzz.com/photos/traditional-home-theater-ideas-phbr1-bp~t_719~s_2107) by Los Angeles Home Media Robert Bliss

Beautiful bookshelves! My choice would be lots of books, interspersed with framed prints, photographs or paintings, propped up here and there between the books (not too small). Nice baskets to hold small clutter. Largish statues. Pots of greenery, etc.
Lynn

"Look at lots of pictures of decorated shelves to decide the look you like."

Since you are asking I think you may not have a lot of 'stuff' so I'll suggest you buy a few rectangular baskets or covered boxes which can hold all sorts of things or just fill the space until you have time to collect some things. Ikea has them but so do other stores and they don't have to be expensive. Very handy for all sorts of items that might otherwise be 'clutter'.

If you have a collection of framed photos or prints they can look good on shelves and take quite a bit of space. Prints can be found in many places ready to frame, photos can be enlarged, or print off pics found online. Inexpensive frames from Ikea, dollar stores, or thrift stores can be spray painted. Intersperse with books, plants, plates on stands, and anything you may have that is decorative. You might even place some of your dinner plates on stands if they are something you'd like to look at. Plate stands can be found in dollar stores. Try to vary shapes and sizes and balance side to side and vertically. Everything has a 'visual weight' depending on size, color, and shape to a degree and 'heavier' (usually larger according to 'visual weight') items usually look best on lower shelves.

I think I would try to find the same style of doors and close in the lower center part so the TV will have a place to stand (or hung on the wall in that space). Also I think the entire built-in unit could be painted trim or wall color.

When the 'busy-ness' of moving in settles down, treat yourself to a walk thru of some of your local thrift and antique stores. You might find something that starts a collection or at least things you like at decent prices. Antique stores are not always expensive altho I know people sometimes think they are. One can find unique items in thrift and antique stores which makes one's decor more personal than just shopping in those big box stores.

I'd paint the walls a mid-tone color as IMO there is too much contrast with the dark floor and beams. However that does depend on your chosen color scheme. Do you have furniture or are you starting from scratch?

You didn't ask but I'd drop that curtain rod down a few inches as it seems too close to the beams. Is that distance a stock length for panels?

I love the last picture that Oly posted. Instead of painting the bookshelves white, I'd paint the FP dark like the bookshelves.

Photobucket is acting up for me, but you can see mine on the "What is on your mantel?" thread. I have a mix of books, photos, small paintings, plants, and items that we've collected on our travels.

Annie--you've got some great mood lighting going there! Is it all coming from the 2 sconces, or are there hidden "puck" lights or something similar in the bookcases themselves?

Thank you all for the suggestions (and photos)! I suspect I am overthinking this a bit. Love Annie's pic and the third pic olychick provided. I will check out the thrift stores as well. I really like the old world style, but I don't have any experience decorating at all. It's hard not to feel a bit out of my league!

Do you think this sectional would look ok in this room?

Please forgive me if this seems rude, but i feel i must address the fireplace issue before considering what to put on the shelves. Truthfully, I did not see a fireplace until olychovk mentioned it. It is so very out of proportion to the shelves. Now, i'd never bring this up if there were not an easy fix. I'm no expert, but imagine it might simply need paneling that wall, adding a properly sized and aligned( with the shelves) mantel and
Painting all in the same shade. Lots of talented folks on here could better advise you on this. Again, i apologize if this idea is out of line. May be just my perception is scewed on my screen.
Marti

Marti, not rude at all! I have no experience with this and find decorating, painting, etc. a little overwhelming. Truthfully, it's not something I enjoy or feel I am good at, so I really appreciate the suggestions and guidance.

I hadn't even given a thought to changing the fireplace or the paint colors, but so many people picked up on those issues here. It's great to have the input of objective (and talented) people.

I think your sectional choice would look great if you keep the dark wood. If you are at all thinking you might want to paint the shelving to tie it into the fireplace more and lighten the space, then it may be a little dark and heavy. But if you darken the back of the shelves like the 3rd pic I posted, or leave them as is, then I think it would look perfect. Some people here seem to be anti-sectional, but I love them. I would take some blue painter's tape and draw the outline dimensions on your floor where you would want to place it, just to see if the scale is right for the room (since you say you are new to decorating). It will help you see if it's too big or too small or just right and where it will fit best.

Also think about whether you will get an area rug and what kind you might choose and make sure the sectional would work with that, too.

I love the look of a small lamp on a book shelf! Along w/all the other great suggestions add a small lamp(for ambience only!)to each bottom shelf~hopefully there are outlets. Hanging smaller pictures on the smaller vertical dividers also adds interest and is unique. Don't overload shelves with too much stuff! Books are really what look best. ;o)

I would seriously leave some "empty" space. You don't have to fill in everything, leave some places for the eye to rest.

summerleah, check out the "What's on your Mantel" thread and have a look at Tinan's media cabinet/bookshelves and also the way the wall around the fireplace is painted. If you like how that looks, it seems like something that would work in your room to tie the fireplace to the wall units, esp. if you could get a darker mantel or ?? Maybe do the accent wall in a tone similar to the sectional you are thinking of? She also has a really nice amount/volume of items on her shelves so that it's not too full of stuff. Might give you some ideas.