It may be one of the hardest things to decide on but art is oh so important when pulling a space together. People are always asking me to help them finish a room and I often hear "It just doesn't look finished." Well that's because you your walls are bare!! I know its hard to pull the trigger on a piece of art (it stands out at eye level and it's expensive) but it doesn't always have to be so stressful.
If you're like me and can't commit to an expensive piece of art, here's a trick I've used in my own home -- designer wrapping paper! If you visit a store like Blick Art or Paper Source you will usually see a section of single sheet, flat designer paper hanging around. They range from colorful graphic prints to large pictorial scenes and come in a variety of colors so it's easy to coordinate with any room. Prices generally range from $2.50 to $8 a sheet -- combine that with an inexpensive frame and you can hang something interesting on your wall for under $50 (depending on how small you cut your wrapping paper).
The print I have above our fireplace is actually just a piece of designer wrap I put in a poster frame as a temporary solution to a bare wall. I've gotten so many compliments on it I've decided to keep it up permanently.
I stopped by a Paper Source just the other day and found these wraps they currently have available. It's always a good idea to keep checking back with them as new papers become available.