I don't think it's a case, when I was in Shibuya in Tokyo I saw a studio in which you just need to give them your phone for an hour or two and they will add those crystals to it creating any design you want.
Of course, if your phone has a case you can ask them to add those crystals to the case but I guess you're not in Japan.
Try to find people who do that, I know lots of people do it by themselves.
Personally I just bought lots of those mobile crystal stickers and I plan to use those, but I think I'll add some special glue (insteal of relying on the one that's just already there).
