I think theyre should be more things to buy with your xp. Things like vouchers or money or possibly spawners. Like 10,000 xp could get you say $10,000 or a pig spawner. And it could get big too with like 200,000 xp for like a blaze spawner.
You should make it into a kind of medival house. Add like a moat on the outside, And a throne with golden blocks scattered across the room for decoration.