I strongly recommend the Legacy_Sonic3_Reskin.zip that "the_swordsman_ps4" (on Discord) and I made together. It's basically a Sonic 3 inspired set of sprites for Sonic. They were used in previous versions in the game, but a few months ago were updated to the most current version. (Actually, I still need to fix his Controls Sheet... I need to get back to that).
You can use them if you like, I don't care.