Unlike most of the commentors, I'm not really much of an Ass man. I just don't find having such gracious baubles to be sexy.
Now if you really want to get my attention, is to have the most beautiful set of eyes. Exotic eyes mostly, like maroon, or shimmering sapphire and emerald. Lavender too, though that's more of a dull color and needs to be presented. My favorite kinds of artists are the ones that despite all the attention they give to the other features of a character, that the eyes are never left out. She's even winking at the viewer, taking such a sexy canting. Those beautiful green eyes caught my attention. And yes, I'm gay.