One of the perks listed is a "small personal art piece". What is this?

If you are a supporter of "Transcendental" level, I'll make you a personal art of your choosing once a month. Why small? Small does not mean "bad" and keeping it small means balancing time, costs and level of quality. Aside from that, it can be anything you want — avatar, commission or a game asset.

This reward level requires you to stay in contact, so keep that in mind while choosing perks.