Last year I did a painting for my granddaughter's room. I ended up with a lot of unused pink paint. So I found an old, unused sketch book and did some quick, silly pictures. (I still had my granddaughter in mind.)
Soon I was out of paint, but I still had many pages left in the sketchbook. I gave myself a new assignment. Fill all the pages of the sketchbook with quick illustrations of whatever was in my head.
Using old acrylic paint collected through the years, I set out a limited number of odd colors and worked until the color on the palette was gone. It took a few sessions, but soon the pages were filled.
Here are a couple more from the first batch, using pink and black paint. You can see a lot of them on this page.