Attached Link: http://munkh3ymagnet.nofrag.com/

Sorry, I was at work and had to get home to Bryce to explain this better. Start by doing a top view render of a good tiling sand dune texture(there are several types at Munkh3yMagnet)on a 2d square and increase the frequency several times.I usually use a square doc. size of either 512 or 1024 px. I then take the render into PS and convert it to a greyscale and give it a slight gaussian blur. I make a terrain with the same resolution as the doc. size and apply the "rounded dunes" terrain filter several times until I get a good shaped dune. I find it helps to apply gaussian edges to the terrain so that it is easier to blend several dunes together.

Then I import the render into the picture section of the terrain filter and blend the dune and the sand ripples together. You can apply smoothing and adjust the height to suit your taste. I wouldn't worry too much about obvious tiling cause you can always add a piece of brush, clump of grass, or a rock to disguise areas that look too uniform or similar. Let me know if you have any questions 'cause I'm not a great tut writer,lol. HTH Dan