When that happens to me I look a tons of galleries. Something will catch my eye and that will be the start of the next project. It may be ideas I see on several pieces that I put togeather in a new idea. I think almost everything has already been created already so you can only improve really on what has already been done. Unless of course you do outragous art like dead rats. Oh wait that's been done! But you get the idea. Don't limit yourself to the galleries here, look all over the web.