In Imagine FX #79 February 2012 hey have an article by James Gurney, the creator of Dinotopia, on tips if your creating & mapping a fantasy world. The issue also has poster to go with the article.
If you can't find the issue in a bookstore you can order it at
this link.
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Here is the preview on the ImagineFX homepage. You can see a little thumbnail preview of the James Gurney article.