I really love the way a big piece of abstract art can add little somethin' somethin' to a room. Observe:
(all images from DecorPad)
Obviously art like this can cost thousands of dollars. Enter art.com. Here are some favorites that I picked out, all for under $25.
I think these would look great framed. Another option is to attach the print to a canvas for that expensive original artwork look. I haven't tried it, but here's a tutorial on how to attach craft paper to a canvas; you could easily could do the same with one of these prints.