I very much like the layout of this map, its quite empty, but as you said, it's a test map.
There is lots of movement available on the Z axis, which i love, and then lots of running room. Your arrangement also allows a greater density of players as thanks to the layering of levels. The smaller platforms also are a good idea in my opinion, as you force the player to jump which makes them more aware and more careful of the environment, and makes them a harder target to hit since they are jumping, and generally an easy target on a large map.
Also: Beautiful job you did with the islands and blending the water to sky. There's a major payoff for that, It makes the map seem bigger yet.
The trim and edges of the structure is also very well done, and very clean.
I think this could go far, I'd like to see what others think too, and maybe an update.
Side Note: The texture your using for the front side of the steps on the stairs is missing. Please make sure to include any custom textures, or list where to get them. OR make sure that you include the proper lines in the config to load the texture. ( As some that are included are not used by default )