Hello Chris, Yes there is an Im-ho-tep (Karloff form the Mummy) model, I think it was released by Horizon. It is long out of production though.
I still have all my original Aurora kits ( I told you I part with nothing) the build quality is that of an 8 year old!! Oh, I was 8 when I did them. I'll post a couple of pics, don't expect too much.
The Mars attacks is a Screamin kit, I thought it was based on the banned cards from the fifty's. Your drawings are first rate, and as you say the one without the helmet is a dead ringer for the kit model. There is a card of the scene included with the kit I'll see if I can find it and post it. It maybe something you worked on.