I finished my backplate project today. The first mold crashed and burned, it never hardened, and I'm not sure what to attribute it to, whether old ingredients, or user error. After 30 hours it still wasn't hard and the instructions said 24 hours would do it. Anyways, I tried a different resin this time, a polyester resin with a hardener, as opposed to the epoxy I tried first.
The polyester resin allowed me to add some dye to the mixture, so I used some blood red UV dye which turned the casting bright pink (like fluorescent day-glo pink). I wasn't too worried about it, since I was planning on painting the back of the plate black and that would darken the whole arrangement significantly.
I used a tester's flat black model paint to paint the back of the backplate flat black, which gave the front a really really nice rust coloured appearance, so I changed my plan slightly and painted most of the front flat black as well, leaving only the raised body portions of the mold unpainted, as well as a smudged/thin layer over the submerged leg parts.
In all, I think it came out amazing, especially considering my level of skill at this.
Here are the pictures of the final product in daylight, I'll take some better night pictures tonight.