It was derived from a original 2 min grid data from NOAA. Have a look at http://www.ngdc.nooa.gov/mgg/image/images.html.
It's original size is 10.5k which was stretched to 16k for the VT version. There are versions with 4k, 8k and 16k available.
The coloring ranges from dark blue (deepest) over green, yellow, red to light gray (highest). There was only preshaded data available, so it can't be used well with normal maps. You may also see some artifacts due to adjacent tiles with different resolution levels. This may be caused by a subsequent refinement process on additional satellite data, showing different states of it at different locations.
The texture also shows the remarakably high aeras on greenland and antarctica. Because of the up to 2km thickness of the ice cover there they're real highlands.
Ok, here some pictures now (please keep in mind that the original is much sharper):
1. Colorful topographic earth
2. The Rockies
3. The Himalaya
have fun,
maxim
...I add some of your works in my catalogu, in the new chapter: 'Cartographies' 
It was bad enough that I've integrated Celestia into my teaching of Astronomy so much that I've had to rewrite most of my lesson plans, but now you're going to have me doing it for Geology and Oceanography, which I also teach. Your maps are great and I am now going to have to incorporate ALL of them into both my class lectures, and as a set of computer lab lessons 
