Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Stellar Sprites Free.
Stellar Sprites v1.2
Stellar Sprites (Version 1.3 – Includes Full Source)
Real-time procedural sprites
Stellar Sprites is a dynamic and powerful sprite generator. It’s extremely easy to use resulting in countless unique sprites.
Do you need space sprites? Whether you are creating a Space Shooter, Adventure, RPG, Trader or any other type of genre, Stellar Sprites has you covered. Drag a prefab of a ship to your editor window and everytime you run your game, that ship, planet or whatever it is, will be brand new. If you find something you really like, save its seed or click the Save to File button and use it later. Stellar Sprites can also just be used to generate sprite files (.png) and you can fine tune them to meet your needs.
:: Unlimited Ships
:: Unlimited Planets
:: Unlimited Moons
:: Unlimited Asteroids
:: Unlimited Suns
:: Unlimited Stations
:: Unlimited Backgrounds
:: Unlimited Starfields
:: Unlimited Black Holes
:: Unlimited Nebula Clouds
Any sprite can be saved to a file if you want to add your own polish to it. Everything you need is provided to get you started.