My kids don't have a lot of options during indoor recess. They can read or they can draw. Mostly they draw (or take the paper and make paper airplanes). All the paper we use for indoor recess is scrap paper - extra sheets from our work or things which were mistakes in the copy room. I grab them all for scrap paper.
In the last week we have had indoor recess quite a bit due to ridiculous heat. Typically the kids draw pictures and give them to me. I hang them up on the bulletin board above my desk for a while and eventually throw them away.
These two I may keep however. In case it isn't clear, the top one is of the life cycle of a plant, something we've been discussing in science. The bottom one is the sun and the eight planets in our solar system.
I love that these kids are processing their learning through art in their free time.