They can do anything they want with it
Starting from "nothing" ending by "limitis of imagination" and "technical limits"
---
example of doing something
roleplayer: I want a lot of flowers arround, as lot as lags become too hard for playing

administration: please provide exact coordinates of every flower. we add as lot of them as possible, 1 flower will cost 10kk of adena and last for a month
roleplayer: I want to have Innadrill castle
administration: try contact current owners (NPCs via administration) or PCs directly, or just take it by force in castle siege. beware that ways to take over
castle in roleplaying territory are dozens, do not expect usual single l2 way.