Thank you all for the kind words and here is the latest version. I have corrected most of the mistakes made with previous work phases and added some more coloring depth.
The original idea behind the spiral formation was to emphase that this represents a fantacy world and doesn't try to be a perfect replication of our world. There are also an island that has a shape of a human skull and I plan on adding several land formations that represents something else.
The heightmap was done using Geocontrol. I rendered over 30 maps with it and combined the best parts into this piece. If anyone is interested on heightmap basics, you find my short tutorial by following this link: http://www.cartographersguild.com/showthread.php?16688