Textures: http://www.spiralgraphics.biz/packs/terrain_civilization/index.htm
Tutorial: http://www.cartographersguild.com/content/116-ascensions-atlas-style-photoshop.html
http://www.cartographersguild.com/tutorials-how/18643-ascensions-atlas-style-tutorial-revised-presentation-actions.html
https://www.dropbox.com/s/6w68cqualb1ciom/AscensionAtlasStyle-Revised-120817.pdf?dl=0
Sample work I created with the above:
http://throndir.deviantart.com/art/Tarmilain-Continent-161144856