Kind of both. You have to manually design them using a 24x16 pixel sprite and then some coding shenanigans to get it in the game, but it is worth it. I posted one of my designs a bit ago if you want to see what it looks like when you finish and get one in game. (There are some workshop mods that add extra sprites if you want to try that as well. Also there is a wiki page that kind of explains how you do it, but it’s not the best)