Prosthetics used with make-up will take a costume to a new level of awesome. The process was pioneered by make-up artist Dick Smith in the 1970s. He applied prosthetics made from foam latex in small pieces as opposed to the earlier standard of a solid mask. His technique allowed actors to have a wide range of facial expressions, appearing more natural. His website sells a course in making and applying prosthetics.
I chose this subject because we recently got an inquiry about making the headdress/hair and wings for this amazing character called Kerrigan from the video game Starcraft.
When you look up prosthetics, you get a lot of horror links. Fangoria magazine is one of the biggest horror publication around, full of film and book reviews and articles like this interview with Paul Jones, makeup FX artist on Resident Evil.
Molded gelatin (unflavored jello) is apparently a good material for prosthetics (haven’t tried it personally). Indie Mogul has a tutorial here.
When we lived in LA we always enjoyed a trip to Cinema Secrets in Burbank for specialty supplies like:
Spirit Gum (an excellent adhesive for prosthetics and decorative doodads you want to attach to skin)
Face wax (to form scars)
Weird fingernail ideas from the Nailolympics
An Impaling kit could be fun