As there will be the hall of echoes, what about a trophy to collect some certain item in the world of D:OS2 and put them in the hall? Like hearthfire in skyrim?

For example: some legend weapons, antiques from some important people, even someone's soul after his death (and yes you can talk with him and ask for some suggestions for your game)

Or perhaps just a place where players could put such a trophy and decide on their own what they consider the most important. It could be a legendary weapon, or it could be the pants of that jerk who laughed at them in prison.

with a possibility to add one/two sentences of player's own description (of the aforementioned pants, for example)

I kinda like the idea, assuming we have a place to call home. I used to collect interesting-looking swords that I'd acquired in Oblivion which I'd hang on the wall of my Waterfront Shack; though that required a mod for it to work effectively (Decorator Assistant, which ensured things stayed where they were put) and it probably had more impact from a first-person perspective than it would from an isometric one.

Larian confirmed that we'd get a "home" in the underworld or whatever they're calling it.

I think it'd be great to have a trophy collection, especially for competitive victories. Eg, if you complete a romance (which only one player can complete per romantic interest), the romantic interest gives you a unique gift that you can add to your collection.

If you kill the guy someone else needed for their quest, you could also get some kind of gift or trophy you could include in your home. It's there for you to rub in the face of your co-op partner. XD

yes, indeed!

"I'd like to invite you into my hall, and be ready for surprised!

I love to collect paintings!

when I saw the fish and pig paiting in D:OS1 I had the desire to steal them and hang on the wall of end of the time

They need do that. Imagine whole wall full of head of killed enemis...