This is a super cute activity that I have done in the past. I print these frames and the kids write their name on them but don't draw anything! They think it's hilarious. They write on a page behind the frame all the invisible things that are in their invisible artwork. The sky is the limit! Some of them really let loose and are so creative! I use Shel Silverstein's "Invisible Boy" poem for the intro to this lesson, and it's always a hit!
"And here we see the invisible boy
In his lovely invisible house,
Feeding a piece of invisible cheese
To a little invisible mouse.
Oh, what a beautiful picture to see!
Will you draw an invisible picture for me?”