It's often a good idea to do smaller illustrations in between bigger pieces. It gives the brain a chance to relax and recharge. Here are some drawings I've been doodling in my sketchbook this week. When I'm doing these kind of drawings, I give myself very little time to come up with a concept for the drawing, I just start sketching whatever comes to my head. It's a really good way to exercise your creativity, to just let the drawing flow to the page without thinking about it too much.