Impressive...most impressive!
I've recently begun planning something very similar and just stumbled across this thread. I've actually been considering a 1/4" hardboard for my wall panels, but the way your melamine boards turned out has me rethinking that a little bit. Now i'm thinking 1/2" melamine.
How large is this room? the space I'm planning for is roughly 16' x 12.5' and it looks like this may be similar...