I've had Wes for a while. I use Wes avatars because he's one of my favorite characters out of all the avatars. I had a very pretty shot of Buffy, but only because I thought it was pretty. My first avatar was Willow, the sweetest shot, because I love AH and Willow (and yes, the pic being great helped). Then I got into a whole string of Willow/Giles pics because I liked they way they looked together.
But I usually like sticking with my boys. I usually connect with them more than the girls (emphasis on 'usually')