Definitely look for a rug that you like. That will cozy things up immediately.

Your curtain isn't quite long enough...it should come just short of the floor. Do you sew? You can add a band of patterned fabric along the bottom. I also prefer to hang curtains/drapes from just below the ceiling, but that's personal.
If you want to dress all of your windows, roman shades or some kind of blind is the way I would go IF I wanted treatments. I love your windows, so I'd probably leave them unadorned unless you have privacy issues. Perhaps something that covers the lower half, then the upppers can let in the light.

Neat fireplace! I'd probably put something cool in front of the mirror that would look good reflected. A big candelabra or seasonal floral arrangement. I would keep the number of things to a minimum so that the shape of the fireplace is the standout. Your idea of a candle fixture is cool, but I think it would be too prohibitive when you want to decorate it differently.

Look for a larger cabinet to set your TV on, the current one makes it all look precarious! :) I'm not a big fan of entertainment centers, so I'm looking for a long dresser to hold the tv, components, and storage for movies and music. Something like that may work for you.

Are you able to rearrange the furniture? The tv in the corner is hitting me as a little off. Could it go where the display cabinet is instead? Then I would put the chair on the other side of the fireplace with the sofa opposite the tv.

Just some ideas, I really love the architecture you have to work with. LOVE the old windows, too!

Chamilla - we share the same birthday!!!
The one thing you didn't mention was your paint color. Would you consider re-painting? I love green, and I love the color of that green planter. Something lighter, perhaps an olive green would look gorgeous with your wood work, and also make both the window trim and ceiling detail stand out. If you hate green, perhaps a soft gold?

Hi Alex and Daisy, thanks for your suggestions. Alex, I appreciate ALL your feedback! Home decor is certainly an area that I'm new to, and it's definitely one of the fun things to do too..Alex, you mentioned about patterned fabric at the bottom of the curtain as well as an area rug...But this is something I'm having difficulty with..What patterns of rug and curtain would go best with this room? Chamilla, I love your idea of painting the walls with soft gold and that's something I'll definitely try. I'll also be shopping for a big candelabra.

Alex, I agree that the tv is a bit off..Would a bigger cabinet on that same side, without changing the location of sofa/chair, work? I mean if we were to change the chair and sofa as you suggested, the coffee table would look a bit off considering its shape, no?

Here's a link that shows what adding a border to your curtains might look like. If you scroll down the page on this link you'll see the pictures. I think I'd keep it a solid color as they show here.

Here is a link that might be useful: Curtain with border at bottom

Chamilla, the coffee table would pivot with the couch. I would keep the orientation to each other the same. Is it possible with the room shape and entrances? The pictures don't show the other parts, so it's hard for me to judge. I think I'm trying to get the tv away from the big window so that when you look in you don't see it. I must have a "thing" about that :) If moving the furniture isn't something you want to do, I would definitely find something longer for the tv.
I may be messing you up because I don't orient ALL of my seating toward the television. I have one or two chairs whose placement is for the ease of conversation. Not every seat needs to point to the tv, since we only use 1 or 2 pieces of furniture when we are alone.

As for a rug, I'm guessing that you like contempory more than traditional? I happen to like pairing the two, but a lot of people aren't comfortable with it.
Here is a link that shows you some samples. Which one draws you immediately, regardless of how you think it will look in your room? First you want to get a general idea of what you like, then narrow it from there with colors and specific design. A rug is an investment, so you don't want to rush into a purchase.

Sujafr has a point about using a solid. That would be easier and you can pick that color after you get the rug. Your choice is to blend or use an accent color. What are you using in your living room for your accent, now? The blue in the glass piece in the cabinet? The yellow in the sofa pillow? Or the green in the planter and keystone?

Here is a link that might be useful: A small selection