I'm wondering this myself. I've tried (and failed) to make it. Can't find any guides that work either.
You probably won't have much luck unless you know someone who knows how to do it. Even then, it's likely they won't tell you. People use lots of custom assets with it, which are bad, and even when they don't use many assets (For example, a placeable mech), it's still pretty secret.
So, they just reserve the knowledge? Well, alrighty then. I guess I'll just look at what the code for the coloring module of ILC does, and try and make do with that. Here's to hoping I don't corrupt my singleplayer test file.
I've been trying to do this myself recently, it seems like everybody's all secretive about it. "I'm a master programmer for 4 years, therefore I can place floran head"
People do tend to keep these kinds of things under wraps just because of how abusable they are when met with the proper mentality/ability. Need I remind everyone of custom drawables and cat guns?