Some people already know about this, but if you don't, BBS has a simple texture editor that allows you to edit pixels on the texture, and save them to a file. Beside that, there is also drag-and-drop support for PNG files when a texture picker is opened.
I think it's pretty cool. 😎
Note: BBS isn't a mod. BBS is a standalone application written in Java, which is designed to be a powerful sandbox for creating machinimas and maps/mini-games. If you'd like to try it out, feel free to join BBS' Discord server: / discord