I think Dirty D had fantastic point (back in like episode 6) saying that all you have to do is stick things together that you haven't heard of before and you have a new niche.
Hmmm... like... I dunno... auto repair shops and sex... I mean, I've seen shoots in car shops, but as a fetish... with the grease and the metal and the machines... that's just an example of something, and I've seen a site that sort of shoots with it, but if you can actually expand on it.. focus on a "fetish" aspect... you probably have something new to market.
I'm looking out my window and I see a beautiful statue (not hot, just well made
). Are there any sex with statue sites out there? Frickin weird, i know, sure... but could you see an angle? Could you convince others you had something new and unique inside?
I can think of endless concepts that "may" work. It's all hit and miss, but if it' off the beaten path then it has to be unique... and as everyone says, that's the first place to start!