I've taken on a project where I draw one new elf character every week. One of the reasons I started this project is because I want to push myself to be more creative and create more content. It's really exciting to come up with a new character every week. I've found that the more you draw, the more ideas you have and the more creative you become.
I've found that it's really important to keep a sketchbook for your ideas. Sometimes I might not even sketch the ideas but just write them down on a piece of paper. Sometimes you may get that feeling like you don't have any original ideas, that's when you can always go back to your sketchbook for inspiration.
I love this quote from Tim Burton. Drawing really is the best way to exercise your imagination.