Where do I get custom computer parts?

I saw on the HyperX facebook page today someone built a 'dishonored' themed computer and I know he just used certain colors, but I saw he had the 'dishonored' logo on one of the parts. After seeing that I looked up game themed computers and the pictures from google of cases were really cool, like minecraft, wolfenstein, etc…

My question is, how would I get custom parts like that (game themed)? Do those people just build it at home or is there a company that makes custom parts?

Pricewatch.com.