Galaxial is a 2D grand strategy game (4X) that features a sandbox mode allowing the player to explore, colonize and conquer planets in vast randomly generated galaxies.
Screenshot taken when stress testing the galaxy generator with 2,000 planets!
I haven't decided on the maximum size allowed yet, but would imagine 1,000+ planets may not be suitable for game play and performance reasons. They look great though.
You can view some full size (4096x4096) versions here:
(Warning: large 4MB images)