I've been puttering around with a custom race for a while now, but now that I'm trying to expand on them, things seem to be breaking in ways that I don't quite understand. However, maybe I can start fixing that from the ground up.
Initially I was trying to figure out how to take a normal creature template (Based on humans for example) and then change all the materials used into another material. There wasn't anything clear on that from the Wiki, so I took from the Bronze Colossus and just made them solid 'material'. After a time, I noticed that certain descriptors weren't appearing when I thought they should, so I added a few body_plan tokens and such, and it appeared to work alright (Of course, I never checked the errorlog, dummy that I am.)
So now world gen isn't working quite right (version 43.03) and as I read through it I see that a lot of things aren't applying due to a lack of bps, and I don't know why they don't exist.
Now I'm thinking it might be better to go back to the first idea, making a normal creature with all the body plans and such, then converting the skin materials to another material, only, I don't know how to correctly do that. I'm considering making a special body plan, but I don't know which things to change to make say, a human with skin made from steel.
I can post my creature file if anyone wants to take a peek and point out what I screwed up.