These are the Duelist and Sidhe Corruptor, respectively. They are troops designed for the game Kingdoms of Camelot and painted with the knowledge that they would appear as no larger than 219 by XX pixels in the game, hence the overall lack of tightness in the rendering.
The Money Pit was a short-lived idea of a building that would produce gold for pirates. Before that, we'd been working with the idea of a tavern where pirates could come in and blow all their gold on gambling and booze and produce gold for the island settlement. The Gold Vault is where the produced gold would be stored. The rooftops of the Gold Vault were meant to be reminiscent of treasure chests.
The Guild Hall went through a lot of iterations. It's the building where players handle their guild interactions and it was fashioned after taverns and inns. This particular version of the Guild Hall was meant to be based in the sea, unlike most of the buildings which were land-based. After I painted the drawing I did, I was asked to make some changes to the design but I still like the original version best.