Could it be possible to add weather effects?
The simplest idea im suggesting would be something like breath puffs, when you're in a cold area for awhile to make the players think "Wow, i REALLY AM in a cold area and not just some snow covered place!"
The bigger part of my idea, though, may be a particle system where rain drops or snow flakes fall from the sky.
Im sure that in the swampy areas of some of the maps players would like to see more of a "Active" area, and not just a "Run through, get the keys, kill badies, get exp" deal. When i say "Active" i mean you hear background sound effects like frog or bird chirping, or if the place is really desolate a slow wind sound along with enviromental effects like:
[u:2up9wl2c]Swamp level -[/u:2up9wl2c] Frogs "ribbit"ing, maybe light rain, maybe a crow "Caw" sound, too.
[u:2up9wl2c]Cave level -[/u:2up9wl2c] Slow wind, maybe some background noise with "rocks falling and hitting other rocks making a echo" sounds.
[u:2up9wl2c]Forest level -[/u:2up9wl2c] Birds chirping, sounds where bushes ruffle.
[u:2up9wl2c]Desolate/Abandoned level -[/u:2up9wl2c] Windy and echos. Maybe tense background music.
[u:2up9wl2c]Temple/Ruins -[/u:2up9wl2c] Tense music all the way, "rocks falling and hitting other rocks", maybe echos and in-human screams comming from the distance. <!-- s:wink: --><img src="{SMILIES_PATH}/icon_wink.gif" alt=":wink:" title="Wink" /><!-- s:wink: -->
[u:2up9wl2c]Other -[/u:2up9wl2c] If i've missed anything, just generally use the rule "What's this place all about?" and stick some BG sounds and music onto it, and see what happens.
It may increase the release date, but it would make SE FAR superior to Korax mod or any other Hexen mod out there...
PS: I think Hexen does have some kind of particle system already in place; in the original Hexen i think there's a tree that has falling leaves that are quickly picked by the wind and tossed at a wall and fall back down. VERY start of game, just befor you get to the green key locked door on the VERY first level.