I think it would be so fun to go mod/urban and just really have fun with it. If it were my shop, I'd want it to be pretty chill: relaxing, and welcoming. I would want it to feel like a modern man cave. A cool leather couch, faux deer head, bold stripes, and a whimsical moustache poster would make the space welcoming and still upscale.

It would be awesome to see some mix of vintage and industrial pieces in there, too. A small flat screen near every chair or a big one mounted on the wall would be good for the waiting area or for all clients to see (I don't know the size of your space).

Hope these ideas are helpful.