Hire out the designer and use the money to retrain the lisp hackers to do something useful?

I'm guessing that punchlines aren't what you were looking for though. You seem to be looking for a problem (a startup idea) that requires a particular solution (4 x hackers with a lisp and 1 x chilled-out designer). That seems the wrong way around to me. And frankly, if ideas are the easiest thing about a startup, you should worry if you can't come up with your own to be passionate about.