I found the most heroic and shiniest possible legendary hairdo once. I very nearly cried selling it, until I realised just how rolling in (un)common shop items I would be from thereon out. And I could never possibly get rid of those, because what if I happened to want to try out a three warrior party all wielding clones of the same somewhat shonky spear in multiplayer just for the lols?
I always sell treasures. I sell duplicate items if I don't think to use more than one, but I keep one of every items, just to collect them.
Haven't sold any treasure yet. I do sell excess items to keep things from getting too crazy in the collection.
All treasure go to earning me gold. I have hardly sold anything else but need to start selling those I have a ton of and keep like 3-4 of each thing at least even junk items as you never know.
So far I sold every treasure I've found except the White Diamond. I don't see the point in selling equipment since it only earns you 1 gold per piece. And if I have the choice between: - 1 more gold on my bank or - 1 more EQ that I could someday possibly use for a new character I'll (at least for now) choose th EQ. Maybe on some point I start keeping one of each treasure. The only thing that bugs me so far is the space it tooks in my inventory. Normally I try to keep some order and that is not possible since it always reorders on closing the inventory.
I will probably keep the Legendary Orc Painting if I get it as it is so cool. All other treasures go straight to the vendor.