Modder RiotEsper has released a brand new mod for Wolfenstein 3D, called Operation: Gral. This mod adds a completely new set of visuals, 22 new levels in total and other additional features. It also retains the classic Wolfenstein 3D gameplay so this is a must-have for all old-school fans out there.
Source: N4G PC Operation: Gral mod adds 22 new levels and improved visuals to classic Wolfenstein 3D