Banjo thumb picks tend to be made of plastic rather than metal, so it seemed silly not to have a printed one! Also, I have a habit of misplacing them, and while they aren't expensive, it's a pain to have to go buy one. This one printed in something like 7 minutes, so unless you live next door to an instrument shop, this is a pretty convenient option.
So, the main issue with printed picks of any kind is that you don't want the layer lines running over the strings if you can avoid it. This thumb pick has been designed to print on its side, so that the layer lines run perpendicular to the strings, to avoid any scratching. This also has the benefit of adding strength to the flexing section!
The rounded part that strikes the strings is intentionally relatively long so that it can be finished with a file or sandpaper, to change the profile in ways that a 3D printer can't achieve. That said, I found it worked just fine as it was (but I'm by no means any kind of expert musician!)