There should be an in-game list of warp locations somewhere. The dome fight area is the nicest one so far I'd say, but more interesting ones could be added, like a sneak oriented swamp as mentioned in-game.
The marketplace is a great idea as it puts together players while their not fighting, and it's very useful. The mines could use some work as it's extremely linear and would be a good map if there were more tunnels and places to go. It looks great, though, atleast.
Consider adding an underground or more covered way to get from the desert to the grass side on the dome. There's an underground area that's quite nice on the grass side but you can't access it on the desert side and as far as I can tell there's only one exit. The reason for this is to allow players who prefer melee to close on ranged players, and players can also sneak under there to confuse their opponents. Sort of like a minature version of the mines underneath the dome.