It depends on what character you want to make. I don't know where i can get templates (or if there are templates) but you can try to open player.dat in slade (which i recommend) and export the graphics as a png to have an ideia of how your character can be displayed. You can use any program, even paint, to design your character (It doesn't need to be perfect, it could be your first attempt). With all said, I hope this comment helped you. :)
I'm making my very first, inspired by Knuckles' new swimming sprites, but I have 2 ideas, one I'm working on right now.
Sonic and Knuckles fusion
Literally flying Sonic (Default or other)
But there's one little issue. I'm not very good with drawing spines on A4A6 and A5 frames. I did manage to lengthen a sprite in order to draw one. I said I wouldn't but I'm currently looking for some help.