1. You notice how your diamonds end up forming lines? Fix that.

2. You use the same ground tile over and over. There's about 3 different variations of ground tiles. Use them.

3. This was a little hard to illustrate, but basically you use a background wall behind the same background wall. Another perspective issue, same as with 1. in the first picture I did. It'll work, but it just rubs me the wrong way.