Thanks for the suggestions, everyone-- some interesting Mods there, which may be useful
None of them are the one I'm thinking of, I'm afraid

The one I'm thinking of, that I had for a little while (before my PC issues), included pre-modified skulls for each non-human race, already set up as helmets, and a spliced tail (similar to what Veg linked to)-- and nothing else :S
Either way, these Mods look like they might be helpful if I can get in touch with the authors, and hopefully work something out

so thank-you for your help