I've wondered about this a bit because most of the fan art seems to be of LavellanXCullen but I think it's Tishna who pointed out that at the time most SS were of TrevXCullen... I think now-a-days it does seem to trend LavellanXCullen or maybe that just more people who played/ing an elf are posting their pics?
I know I feel a minority sometimes, Trevelyan non-mage romance Cullen but each to their own. I have a mage TrevXCullen in the works atm
I think a lot of the people who prefer to play elves went with a Solas romance first. I'm seeing a lot more LavXCullen ships now. I mostly noticed because I had to wait for the game and was living vicariously through everyone else's SSs and videos (my Dalish is now at Skyhold and finally starting the flirts that he returns a little) 
I played all the way through two Suranas in DAO but could never make it more than about halfway through an Amell PT for some reason (I'm changing one of the Suranas to an Amell in the Keep, though.) I just didn't personally find playing a human all that interesting in DAO (I generally find humans less interesting in fantasy games, but more so in DAO with a fairly predictable avenge-my-betrayed-family background); I only made it through Cousland PTs because I wanted warden queens. I actually liked the idea of a BAMF S&S professional soldier Trev for a Cullen romance, but there's so little connection to background. Honestly, 3 games in a row, the humans have been nobles; at least in the other games it was an important part of the human's story. I'll probably eventually create a Lavellan warrior or rogue for him because I can imagine much more interesting interactions with those.