Sure, you've used caulk to seal around your bathtub and baseboards, but have you ever thought to use it as a drawing medium.
Last week, I brought enough plywood from home, for each of my students to create an image. They sanded and painted the boards a solid color before drawing their image in chalk. This was then traced in caulk.
After the caulk dries (it takes maybe 3 hours, so we waited until the next day), the paintings are ready for more layers of color. Most everyone kept their background color the same as their underpainting, but one student, kept her original pink board color for the flowers and added a layer of yellow latex for the background. I love how the brush strokes create visual texture to compliment with the caulk texture.