I found some zips of planets provided by the awesome modders here! The three zips have great looking planets in them but I believe the one you'll be most interested in are the Graphic Enhancement Mod (GEM) by Martian and New Planets standard res as that's most of the samples I think that were shown here and most of the ones I use. Feel free to download from my Google drive! As Igard said all credits go to original creators, if I missed anyone let me know:
Creator - fungun
Creator - Zhar2
Creator - jestr
Additional Textures, models, addons - Cormoran, Don edwards, 3d duckboy productions, 3d.concept40.com, John M. ,Dollan , Andy Roberts, Steve Bowers, Ivo Beckers, http://galaxistar.googlepages.com, Matt Davis, Selden Ball, Runar Thorvaldsen, Rob Sanders, Cham (from Celestia forum), Pericapolis, Fridger Schrempp, pioneerxtower (J. P.), Bruckner, Shcuf, Jean-Marie le Cospérec
Thanks to Baleur for supplying the Eve planets.
Barren Planets by ConflictX.
Additional planets by Kalthaniell.
New Planets standard res.zip
GEM v2.4 Icon_Updates.zip