Parts of it is a copy of known Moria art (be it Alan Lee, LoTR/Hobbit movies or video games). I will post more pics later showing gates and halls that are finished.
The parts that are only in style of dwarven in-mountain builds (a la Tolkien and post-Tolkien fantasy) would focus on use of rock, stone and refined rock plus decorative stones. I use gleam for lighting purposes.
The likes of machine rooms or smeltery are made with use of metals (machined copper/iron).
Important parts like a vault or throne room will also have gems and silver/gold to show off the riches of mining folks.
Settlement growing outside the mountain have freedom of style - whatever other players feels like building is cool. Its more like an addition to the actual Moria - settlers drawn by reputation of Moria will come and claim land for themselves and use help in building and progressing (and that help is always provided: be it tools or some resources or advice and information about where and how to mine or hunt etc.)
The Secret Passage being an adaptation of very well known “Speak ‘friend’ and enter”: Less gloomy than in LoTR as my Moria is an inhabited version rather than an abandoned ruin infested by orcs, goblins and trolls (should I even mention Balrog? ).