Pictures can be a great way to add color to your room! One of the ways I've done this when I didn't have a lot to spend was to go to my local Goodwill/thrift store (or yard sales too now that spring is upon us), and look for a book (or magazines) with pictures I liked and could easily cut out. Then I looked for frames, and took them home to paint. Just take the glass out and clean them up, then lay them out on a drop cloth or newspaper (outside on the lawn is best) and spray paint them in whatever color you chose.
To figure out how I wanted to place/group the finished pictures on the wall, I got pieces of scrap paper, which I cut to the same sizes as each of my frames, then taped them up on the wall. Using blue painters masking tape works best, because you don't take paint off the wall as you move them around. When you get the placement just the way you want it, hang them one at a time as you take the papers down.
Hope this helps!