You know what I really wonder, though? Not even the NPCs can be gay. Nowhere in all the galaxy have I ever seen an indication from background NPCs that they might prefer a lap dance from someone who isn't a woman - or that they be wanting to be chatted up by the lady in the Mandalorian armour, rather than the sleazy wanna-be smuggler who just dragged himself out of the latrine. That takes an outstanding amount of effort and forethought, I say.
If nothing else, when Bioware said "gays don't exist in Star Wars" they meant it.
There is a human female and twi'lek female dancing together on Tatooine.
Not sure if that counts.
Most NPCs seem neutral as far as sexuality goes....can't tell either way.