Hmm its a very open brief... I guess finding out what the wig is, and how its going to be trimmed, as per style and colour, may be helpful, or a least suggest something... I guess its safe to say that something feminine wont upset him... guess we just need more information...

Although I figure its safe to go for something flirtatious/fun... eg a cat, they tend to be quite feminine and they leave a lot of play space. Younger guys who are either good looking or think a lot of themselves tend to like that sort of costume, its easy on the prosthetics too, because theres a lot of nice cat 1/2 masks, and with halloween being fairly soon it could be good to keep an eye open you can always customise one if need be to match the makeup you have in mind. not sure if this is helping at all...