I am not really sure what this is for.
If it is just too goof off, or meant as a quick build, it is perfect.
If it is meant for a movie or something, it is perfect for a quick scene.
If it is meant to show skill, it needs to be a lot bigger; there is no way that you can add any professional detail to a build that small.
If it is meant to be an RPG, it needs to be a lot bigger.
If it is meant to be a DM, it needs to be at least slightly bigger, needs more cover, and it would be nice to have a secret passage or two.
I need more information to make good suggestions. To me right now it just looks like a quick, goofing-off build, and I am not sure as to why you posted it.