I'm a writer who has created several different science fiction worlds. Naturally, I've needed to make maps for my own plotting purposes. So far, I've not shown them to anyone else, depending on my narrative skills to build the images in the reader's mind.
I've been using The GIMP and Inkscape for awhile now.
I love the JPL landsat images so I searched through their archives, found some shots that seemed to match the images in my head, then cut, pasted, and blended until I had the alien coastline I wanted. This is the result.
Click image for larger version. 

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