When me and my mate did our FAA CPLs, we did it in shorts and T shirts - ocassionally Hawaiian shirts.
When he did is JARboy CPL he had to wear 2 stripes, shirt and trousers. He said that he felt like a right tool but it was good for pulling the girls
He was going to get two sets of 4 stripes and sow them together and turn up wearing 8 bar epaulettes - but he feared that the humourless bstards would have thrown him out
...And no, I'd never wear epaulettes in a light aircraft unless it was a company rule and I was flying fare paying passengers.