I don't think you're making good use of light/dark contrast, which is a very important compositional tool. take this image into an image processor and change it to grayscale and you'll see what I mean -- everything looks a little.. muddy, almost. This is not always the case, but as a rule of thumb you want your image to look awesome both in full colour AND in greyscale.
Also, I really think you should dedicate some time reading about composition. Here's something pretty useful (I think it could be from an Andrew Loomis book, but I can't recall): http://i.imgur.com/QhVBh.jpg
Overall, considering both the colours that you're using and how you arranged the subject matter, it feels like you were playing it safe.
Otherwise, I like the simplicity of everything in this image, I personally have a lot of trouble getting things down to their bare elements.
Thanks, great feedback. Adjusted the colors of the buildings and redrew some cloud parts.
This is quite neat in its simplicity, I like how the city expands vertically. It's a bit low in contrast though, maybe add another darker shade to the bottom of the island? Also, using slightly different colors for the city/island would enhance the piece. (I see you re-used the clouds from another of your images..so if this is intented for the challenge you may have make some changes/new clouds...just letting you know while there's still time to fix it). Nice name :)
Great!!