To start with, choose one or several colours for your background. I chose two shades of purple as my primary and secondary colour (bottom left). Then I used the gradient tool to create the sky.
I wasn’t happy with it, so I changed the hue.
Then I used the paintbrush, 5 points white, to dot the sky with stars.
Then I used free plugin Starglow to make the stars shine.
You can tinker with the length etc of the “spikes”, and you can choose whether to add the diagonals (which I did).
I fiddled a little with the Mini, Maxi and Radius. Don’t ask me what those mean. You can trial and error your way to a kind of star you like.
And, um… done! 🙂