What's a Hot Niche Right Now (Solo Content)

So I am working on creating a new network of paysites... yes even in 2014 (well actually more like for 2015) instead of the solo girl sites we've done in the past, I am looking at a more niche market...

I already have several sites lined up (none live yet...)

SniffMyPantyhose.com

JOIAcademy.com

RestrainedTeens.com

GeekSluts.com

SmashThatPussy.com

But as I have some shoots coming up, and have enough time within them shoots to probably shoot 1 or 2 scenes for a new site, wondering what Niche is hot right now... ? Any suggestions...

I was thinking of a messy site, like with the girl covered in some sort of gunk... but not sure how relevant that is nowadays...