Egg carton mania

Alright, so I have a problem. My mom asked her friends to start saving me their egg cartons, so that I can use them to mix paints in.
This was very sweet.
Unfortunately, Styrofoam egg cartons do not work for paints, because they are not air tight. No matter how tightly I wrap them up, my colors dry out.
My mother keeps asking her friends to bring me more of them, because she's still convinced that they should work.
This has been going on for almost 6 months.
I now have over 200 styrofoam egg cartons of all colors and sizes, and it's to the point where they're filling up my closet, there are stacks of them everywhere, and my mom still brings home a bag full of 5 or so more every single week.
I know that I have to recycle at least some of them, but does anyone have any ideas of craft projects I can do with them?
Here are ones that I've already done:
Ring holder
Fairy light revamp
brooch backing
Organizers

Any ideas? Any at all?