I keep thinking, you can't really be bi if you like only totally feminine boys dressed as girls etc.
That is because of the image, you are (technically) pansexual by that nature to a certain degree, maybe gay, but certainly not bi, because the image of boy is subjected to a girl-ified state, hence your focus is the feminine presence on the boy.
I may be thinking too much.
I think most people could be considered pansexual, but more specific definitions lose the subtle nuances of variety, in favor of being more specific.
As for your specific example, I like to think of each preference separately and try not to overgeneralize. Really, the label is irrelevant if you know what you like and don't like, and you are able to inform others of that fact, even if it takes a lot of words.
I think if you enjoy both sets of plumbling, then you're bi. It doesn't really matter how "masculine" or "feminine" they appear.
The only problem with this definition is, again, it's horribly unspecific. Saying you're bi might make the wrong implication that you like both girly girls, and manly men, and you might not want to make that impression.
Then again, being 'straight' and 'gay' doesn't necessarily mean you have no preference on looks/appearance/traits as long as they have the right plumbing, so...
BLEH. This is why I hate labels on sexual orientation.