A user on Reddit, u/Ledgamedev, has created a tileset generation tool for game developers called Tilesetter. The creations made with Tilesetter can be exported directly to Unity, GameMaker Studio 2 and Godot.
According to the website, Tilesetter is fully customizable and comes with a free "lite" version and a full version that costs $12.99.
Tilesetter is available on Steam and Itch.io. They also have a community Discord.
