Instead of buying a pricey piece of art from a gallery, why not create your own piece? Framed patterns can complement a room just as well as an artist's print. For example, check out your local fabric store for patterns that could be put into an inexpensive frame. Wallpaper and even wrapping paper can also be framed.
If you have any artistic talent, paint your own pattern. For example, for a contemporary look, run blue painter's tape across a canvas to create angular shapes. Paint those shapes in alternating colors, remove the tape -- and voila! It's modern art.
Also, consider framing your post cards and photographs. Photographs are inexpensive to enlarge and print from your own computer, and they tell a story about your friends, family and travels.