This is a question that comes up way more often than I would have guessed. The short answer is that it's possible, but why would anybody want to do it? It generally requires at least a couple of different spoke lengths. I'd have to guess at those. I imagine spoke tension variences are going to be pretty weird too. Other than as a desperation measure or just to show off that you can do it, I can't imagine why anybody would want to.

Most folks who build their own wheels do so because they want to build the best, most reilable wheel they can produce. If that's your goal, starting with mis-matched components isn't very smart.