I kind of like them as they are. If you want to inject some color, you could paint the rear of the bookcases a different accent color, e.g. a dark blue (or whatever works with your furniture). You could also wallpaper the rear of the bookcases, too.

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I LoVE the wallpaper, want sure if it would be too much with the rock fireplace. Also, I have wallpaper in my dining room.

ok, thank you!!!

now, what do we pick for wallpaper?

SO hard to decide.

Or paint the backs same as the walls, which harmonize very well with the fireplace stone. Not sure about wallpaper either since the stones have such a strong, bold pattern.

If you won't live there forever, attach the wallpaper to the back of the shelves with tape or some other means so it can be removed easily when you go to sell the house.

A fresh paint color on the back of the bookshelves would help a lot, especially if you don’t have much color in the room. You could also pull that paint color out and repeat it with pillows or accessories. I would also rearrange your bookshelves, and instead of having one object displayed per shelf, such a picture frame, I would incorporate plants, books, small art, etc. to make it more interesting. There are tons of examples of bookshelf styling on Pinterest if you’d like to make your bookshelves look more stylish.

Totally agree. so Hard for me to design these shelves

keep them white as it is timeless and classic. paint your mantel (the piece above the fireplace) white and i would paint the facade white too. as for the back panel? once you paint the architectural elements white, you can pick a color that makes sense to your over all pallet of furnishing. since you did not provide any overall pic of the room, cannot tell you what shade would be the best.