Quakewiki has a copy of QuadQuake, a partial conversion from 1997, available for download:
Quadquake makes extensive changes to the original game. There are new weapons, there’s a third-person camera, and it’s possible to play as an ogre or a death knight.
The maps included in Quadquake are all maps that had previously been released in 1996 and early 1997–for example, Critters by Jim Lowell and Death’s Taste by Utah. One of Quadquake’s maps is not in the Quaddicted archive, however: Marsalis by Noel Weer, from February 1997.
If you want to create a listing for Marsalis, I used pak extractor to rip the file out of Quadquake. The Quadquake release notes include copies of the maps’ original text files, and I bundled Marsalis’s text file together with the map as a zip:
I don’t know if the version of Marsalis featured in Quadquake is the same as the original map. The Marsalis text file states “Authors MAY NOT use this level as a base to build additional levels.” but Quadquake changes some of the monster and ammo placement in Death’s Taste, so Marsalis may also be modified. I think the text file is accurate, though, because the Quadquake release notes don’t edit the other maps’ text files at all.