I assume it's more like other spiritual dimension, rather then something materialistic (like Dwarven
Halls).
His
Halls might be 1x1 meters (or less) in materialistic part of
Valinor, but still be gigantic for every
elf, that lost his body, and enters it.
Dunno bro.
I am personally more curios what are elfs, that are in it, doing all the time? Are they allowed art, or they are just forced to stay and stare at some empty non realistic
walls?
That would be pretty unfair, because there is
Feanor, and there is also
Fingolfin and many noble
elves. You can't judge them all equally to boredom for thousands and thousands of years, without any selection.
There must be some layers of it (like heaven and hell) where more noble elves are allowed some (creative) stuff to do, as opposed to elves that were bad.
Maybe Feanor is forbidden to meet anyone, and do any kind of craft or art, and some elves are allowed to do all kind of fun and creative stuff.