I often leave art supplies out for a day or two after a project so that Maia can continue working with whatever materials we were using. I realize this is thanks to the luxury of having a dedicated art space. But I do think it is a wonderful way to encourage creativity. Even just a table dedicated to art for a couple of days would work. When I do this, Maia will often turn out variations on a project or a completely unique approach (for her anyway) of using the materials.
The other day the liquid watercolors were still on the table and Maia asked for the jar of cotton balls (yay for see-through containers on the higher shelves!). She began by dipping the cotton balls into the watercolors and dabbing them on paper, then started methodically dipping the balls into the paint and setting them on the paper, forming a circle. She left them there for a while before removing them. I love how it looks. Maia didn't put any name to it, but my overactive grown-up mind thinks this would be a fun way to paint caterpillars or holiday wreaths. Or completely abstract designs! It also makes me want to bring out the q-tips for painting with watercolors.
Oh, and this leaving art materials out thing? It's really just me being lazy and calling it something else.