Before there was Mario Maker, there were hackers that made level designers available for old mario roms. In 2007 I started messing around with these and made a few rom hacks, mainly "Super Mario Bros: Jerry's Remix" which was really the only finished one (almost). Among a few other attempts were "Super Mario Bros 2: Another World" which was a one level deal, "Super Mario Bros 3 From Hell" and "Super Mario Bros 3 Pink Version." There was also an attempt of a sequel that was halfway made with more standard levels called "Super Mario Bros: Jerry's Remix 2". After all this I pretty much stopped. I've always wanted to use some of the graphics tools and do a full overhaul starting with some levels from scratch.

Also, there were a ton of other roms made by much more talented designers here as well as more all over the internet.

jlehrjr.itch.io/mario