Just got this Gehenna album and am loving it -- now looking for some other laid back black metal similar to this album and with a somewhat related type of atmosphere/mood/production/etc.

I'll think about it, but I've never heard anything else like that Gehenna debut. Dimmu's first is similarly "laid back", but the atmosphere isn't remotely similar and frankly it sucks anyway.

"Shivering Voice of the Ghost" is magnificent

I recommend the Wanderer part of the Wanderer/Wintermoon (two Finnish bands) split CD. The sound quality is rougher than on "First Spell" though.

that split is awesome!!

forest of witchery by Thy Seprpent i think has a similar vibe to first spell, except i think thy serpent is much better...coincidentally thy serpent and wanderer have some of the same members

Yeah that Thy Serpent album may be a good option. Very enjoyable anyways.

A bit of a shot in the dark but maybe Midvinter.

malignant eternal - tarnet (1995), awesome melodic black metal with such an evil atmosphere.
isvind - dark waters stir (1996), one of the most unknown and underappreciate gem from norway with great sinister melodies.
kvist - for kunsten maa vi evig vike (1996), the sound is very dark and malefic.

Try Covenant's (nor) "In Time's Before The Light", great album before they went all fuckin weird.