I know that you want framed art, but just in case you are willing to consider wall murals, go to
http://www.wallmonkeys.com/
They are peel and stick vinyl and can be pulled and reapplied. We have a large (72 x 48) wall mural of hot air balloons and rainbows on our toddler twins bedroom wall. Most can be one of about 8-9 sizes from 18x12 up to the 72x48 size that we have. And they are reasonably priced. For just this theme, we had hundreds to choose from. You'll find many, many options for what you want there.