Planetary screen savers for unix include the original xearth , and the satellite-photography enhanced xplanet , and xglobe . The most beautiful 4096 x 2048 pixel satellite image of the earth on the Internet is on the Official OpenGL Solar System page, provided also by The Living Earth . Therein lies the rub. It might be hard to justify dedicating that amount of disk space for occasional use of the highest resolution data. My current versions can compress the above 1.86624 GB file to under 150 MB, and still yield binary exact comparisions after expansion.
Work continues on better and faster algorithms.