Hey tilli,
I agree with mattn, it's a very nice start. If you don't know what he means about the terrain feature,
look here. If that doesn't make any sense, let me know and I'll give you a demonstration.
You've done a really good job of managing the dimensions and the map shows a good eye for getting those things right. It's really easy to mess that up, so it's obvious you've been planning and not just throwing brushes around.
I've attached several images. One of them shows you what mattn was talking about with doors missing the "upper brush". They need to show the wall above the door.
Another couple show you things about the textures. I thought the brick texture could stand to be scaled down. Also, you use flat textures for most of your walls. Even though we often see our interior walls as fairly flat and white, there's actually a lot of color variation and texture going on. If you use a totally flat texture, it can often make a wall seem fake, so it's usually good to have at least some texture on a wall, even if it's subtle.
Also, walls tend to have borders on the top and bottom that help "glue" them visually to the wall/cieling. We don't have many good interior wall textures at the moment, so you may not find what you need. But if you wanted a simple, light-colored interior wall texture I could make that for you. I would think it would at least have a runner board on the bottom and maybe a bit on the top.
Overall the construction is good and you've made good use of prefabs. But if you want to go a bit beyond just walls and prefabs, you should start looking at doing a bit more brushwork. The final thing I'll attach in the next post is a big image with an example of how you can start to add more detail through your brushwork.
Again, nice start! With a bit of touchup this could definitely be a skirmish map. And don't be afraid to venture up the z axis. It's not as hard as it may seem.
