Right now it seems the Superheroes franchises and Star Wars themes are the most popular. Probably because of how the movie industry is at the moment with a lot of superhero movies being dished out like it was going out of fashion and of course with the much anticipated Star Wars Episode 7 that just came out.

Also a lot of the TV shows that are currently running tend to give people the most ideas for an Alternate Universe fandom. 

You could try to search key words but I myself have better luck with 1x1s as you're not waiting for weeks on end for something to happen. you can cater to one person easier than five and can give it that more personal touch via more frequent communication. 

I had my very slow days easing into the Guild back in 2012. Eventually you do come across little gems of roleplays. ^^

Trust me, it WILL happen.