Clear contact paper, leaves (or colored paper), kid scissors (for cutting contact paper, and for cutting colored paper if you choose to use it)
Create a collage of leaves to hang in the window. Cut two sheets of clear contact paper to desired size (a square 8' is good). Peel back paper to reveal sticky side of one sheet, and stick on leaves, moss, etc. of various sizes and colors. Then peel and place other sheet of contact paper over it, and you have a collage you can hang in a window. Also works with cut paper pieces if leaves aren't readily available.