I cut frames from colored paper (thanks Jen!) and then cut contact paper to fit. This was a great tactile experience and the littles had fun exploring the sticky surface. When I did this with 2's and 3's they randomly threw confetti and die-cuts on - but my 4's were very deliberate in their placement. (I love this one where the little gave each chick a flower - some one to one correspondence going on).
I found the stickers on sale at Michael's. They are on a black velvet background and the littles colored them in with markers. They absolutely loved these.