I still use MS Paint and never had any issues with it. I guess I got used to changes easier than other people. My friend DarkVampireDee uses it as well and his Sonic tilesets are amazing. One program I've seen others in the community use is ASESPRITE, which is a pixel art tool. I would only recommend GIMP and Photoshop for things like Doom sprites.
And BTW. Those Badniks are by me, and were made long before Tom Payne shared the official files containing the set of scrapped and unfinished sprites.
And BTW. Those Badniks are by me, and were made long before Tom Payne shared the official files containing the set of scrapped and unfinished sprites.