Leather is an interesting material to do pyrography with albeit one so expensive that one reason for me to buy this wallet to give it a try was the hope to offer it in a silent auction at a brony meetup very soon.  
I found one must be particularly cautious when doing pyrography on leather for it darkens a lot faster than wood or cork (the latter burning faster than wood). We are talking of splitseconds here so using different shades is a challange, but an interesting one. Another challenge that leather provides is that unlike wood or cork it is a rather yielding surface (at least in case of this wallet rather than I expect just a one layer piece of leather would be).  
I burned the stylized royal sisters from the first episode onto the front of the wallet and the symbol for the Elements of Harmony on the back.