Messing Around With Shapes
When I'm too tired to actually "draw," maybe when sitting on the couch with a beverage or in a particularly slow meeting, I'll bust out an old "art school" exercise (I didn't go to art school so I'm just guessing they do it there). You fill a page with random shapes, look through them for images, then render them out. It's not quite a no-brainer but it's cognitively very light and pretty fun.
Unfortunately I don't have the "before" for any of these pages to show, but here's a page all ready for exploration.