I'm looking for stuff that has a strong foot in traditional black metal, but at the same time has a lot of mellow/acoustic parts. I guess something along the lines of Imperium dekadenz, but where the acoustic guitar would be more prevalent. http://www.youtube.com/watch?v=z15AhLwQ2jM

Agalloch?

Try this band called Under That Spell. Their debut is an excellent, excellent album and they have many acoustic parts woven beautifully into the songs, not just a folky strumming intro and then hissing guitars all the way.

Huge Agalloch fan. Thanks though.

I'm feeling this. Also I take it OSHIEGO is your band? They sound amazing!

Nychts is hands down my favourite.
https://www.youtube.com/watch?v=LR3auZSPzqI
The use of acoustic guitars in the mix is both subtle and effectful.

I also like the band Morose when it comes to acoustic guitars in black metal.
https://www.youtube.com/watch?v=HuXm3TdUZbc

If you can get a hold of it, Hagal's album, Karg is pretty good black metal with lots of acoustic parts, including some nice sections where it's interwoven into the more standard riffing.



Another wonderful album with some lovely acoustic moments is the Belorussian Karaczun, with their album, Хаморлівасьць. It's been re-released on CD, shouldn't be too difficult to find.

I imediatly thought of Falls Of Rauros' album Into The Archaic

http://www.youtube.com/watch?v=k9bGEIfESHE

I highly recommend secret of the moon's unearthed arcana demo. best stuff they ever did, three thrashy black metal songs with plain beautiful acoustic interludes.

only one example on youtube though:

Haha, they have an album called Black Sun Zenith, a reference to the Magic: The Gathering card that came out earlier that same year. A bit hard to take them seriously after seeing that, but I'll check them out, they sound cool.

Also, for the OP: May be too folky or too obvious for you, but check out Wyrd's Heathen. It's a 51-minute song/album of glorious acoustic/black metal.

Satanic Warmaster did an acoustic rendition of Burning Eyes of the Werewolf that might fit the criteria.
http://www.youtube.com/watch?v=4jCGDTmboeE

Dornenreich's early stuff makes great use of acoustic guitar sections, a bit like early Satyricon.
Haven't heard the later albums & can't say to what degree they can still be called black metal.

You should listen to Aeternus album which is called ... And So The Night Became. There are few best acoustic moment which I've ever heard. Also try TENHI - Kauan and second and third albums of EMPYRIUM.