Google "Wild Bunch holsters" and you'll find many images of similar holsters...named after the movie.
When revolvers were being replaced by semi-autos, mainly 1911's, these type of holsters were worn by military and LEOs. wild bunch holsters - - Yahoo Image Search Results
If they have a lot of bling, they may be called Bar-B-Q rigs...I think the Texas Rangers came up with that one.