I skin for IPB and once owned a very small free skinning site. Skins are what people want and there are so many forums out there that it's a good chance of being very successful provided that there are numerous, well-designed skins and discussion and support to go with them. You might also want to include a Paypal donate button, there are generous people that use free skins that will donate.
Good luck, keep us updated if you decide to follow through with the plan!
