I remember reading in one of Richard Dawkins' books about the theory that a certain small percentage of homosexuality in a population (not necessarily human) contributes to species survival. The idea is that the homosexuals would devote some energy to caring for children and doing other "domestic" tasks for a relative. It's conceptually like the idea that a certain amount of infidelity by females is a genetic "side bet". Many of Nature's solutions aren't obvious or linear.

The idea of homosexuals contributing to childcare is directly illustrated by a gay stereotype you didn't mention: The "eccentric" aunt or uncle who dotes on a sibling's children and helps with babysitting and other parenting tasks.

As for a connection between creativity and homosexuality, the answer may simply be that homosexuals can devote energy and resources to the arts that a heterosexual would have to budget for childrearing. Homosexuality occurs in other species besides human, and it's hard to see a connection to creativity in those cases. Do homosexual birds build fancier nests? Or gay beavers fancier dams? Not as far as I know.

--Robert