Well for Earth or Mars that didn'T prove too much of a problem since the terrain datasets are available without charge on the web. There are also some textures helping in this process, though for a green or blue Mars a bit of extra work is necessary.
The following two images show Earth as it might look like from Space in a thousand years from now.
And here is MArs - currently the Capital of the USC - as seen from space around 3030 AD.
More Challenging are worlds where there are no elevation datasets available. Why this could be a problem? Well because there are now two options to be considered. Is my actual goal to have a single illustration of a planet (which could be drawn as some kind of matte painting)? Or is it to have a 3D model to use as I please for future images too? The latters seems more appropriate for me.
Here is an image of Altara, the fifth planet orbiting Altair, which is one of the cultural and economical centres of the USC. As visible the texture is considerably less detailed than the ones derived from actual data and I reused Earth' cloud layer texture here. In addition to that mos of the coastlines haven'T been worked on and still show the old linedrawing shows through:
Well thats it for today. Please leave a comment I you are inclined to and like to share your ideas.