This was the part that I struggled the most to visualise but I think there have been some great suggestions. A cape seems like a good idea but for me, sticking to the classic meeple shape is quite important as we represent the game that first introduced that shape to the boardgaming world.
So, my favourite ideas are either a robbers mask (covering his eyes like in the picture above), possibly with some thick stubble too as we all know that robbers don’t shave very regularly as they’re too busy out robbing and stuff, or a big bag of loot/ swag by his feet to prove that he’s had a good day of robbing. I think either of these could be designed without changing the overall shape as the bag could be in front of his feet.
PS - just in case it isn'the clear I was suggesting one or other of these two things rather than both