Yes, I've forked a version of SonLVL for the levels. So theoretically you could make your own ones. The only wrinkle in this, is that I also use the level editor to 'tag' objects for the rendering engine so it understands which optimisations to apply. The levels will work if you don't do the tagging, but run more slowly. So the process is potentially a bit more awkward than it is on the Megadrive.