I'm mainly trying to keep to a world where different species are of broadly humanoid form, like for example Mass Effect. There are a few reasons, such as to minimise the need for specialised areas and equipment on the ship (in keeping with the corporate mentality of cutting every corner possible). I'm also not too much a fan of multiverse crossovers, personal preference on my part.
Anyways, thanks for your interest and I hope you find another thread for him. If you decide to come back with another character, you'll be more than welcome.