Mine seem to like the corner where my preskimmer box, heater, and a powerhead all come together! At least thats their prefered place to sleep.
But, yeah they'll host in things other than anemonae. I've heard of people having success with clowns hosting in frogspawn, hammer corals, and torch corals to name a few. I have a frogspawn (and other corals) and my clowns totally ignore all of them and just swim around the water column.