I HUGELY disagree with your intentions. It all depends on your view of "uncommercial".
On that note, I would also like to add Coil's "ANS", which is a 3 hour or so drone album.
the thread is asking for the most uncommercial albums...a black metal album by a black metal band is directed at a certain audience; therefore, maybe not as much as a radiohead record, it still is commercial. could i make myseld clear this time?
here's another: