Well, if you only care about making tilesets, Pyxel Edit should serve you well at $9 USD. But, if want to get more out of your pixel art, definitely consider Aesprite. But, if $20 USD is too much, there other alternatives you can find.
Aw, I'm really touched you found my small jam game worthy of your collection. I'm currently expanding on a different game, so I'm not sure when I'll expand on it, but I will consider the possibility of a bigger game. Thanks :)