An old pic I made a while back.
Landscape version: https://www.newgrounds.com/art/view/homerboy4/aurora-space-background-2
It's amazing how using the Blend & Fuzzy Select tools, followed by Smear spam can create such a simple, yet beautiful aurora effect.
Feel free to use it as your background.
You are free to copy, distribute and transmit this work under the following conditions: