Got a few points to make.
1. Yes, this thread will make an excellent WIP thread for your new map so make a start. try to move it as far as possible and then when stuck, ask away.
2. We may have to remove that map cos its a WotC map and copyrighted. If you can provide a link to the map on a WotC site or whatever then can you edit the post.
3. CGTextures is a great resource and I like it cos its easy to use. You can use the textures in commercial and non commercial maps but you cant use them in creative commons maps or any maps that have a license that makes the parts of the image free to use. So not CC or GNU etc. They specifically dont allow scrapbooking where you collect up the textures and repost them online as a set of textures - thats their big no no. But as long as you cant extract a good version of the texture back out of your image then I think your basically ok.
4. I wrote a seamless texture tut here: http://www.cartographersguild.com/sh...ut-of-anything which is basically the process tilt is describing.
5. You get get a GIMP plug in courtesy of RobA (I think he has a link to it on his sig) to do that process or in that thread is a script which will run it automatically using image magick. Otherwise its a bit of a chore by hand.
6.