i was bored and decided to surf moddb.com for mods that i wasnt aware of. i found a couple (which youve probably knew already, not yet added in the Mod-Addon section though)
Heretic 2 Siege - http://www.raven-games.com/hosted/siege/
The Heretic Fortress - http://thf.raven-games.com
shame there arent alot of mods for this game