Those are Glitterado Nebulae. I as space-artist recognize these arithmetic procedures from self-made nebulae.
You can get endless of these at www.flamingpear.com, where you can get as well LunarCell for planets, Solarcell for suns and Glitterado for nebulae. Just hit the dice on it's interface and you'll have a brand new Nebula/Star/Moon, with sliders to play along with and colors to choose
Hope you enjoy!
PS. Oh if anyone wants something custom made, I'm new here and willing to try and create space scenery for games. I'm helping with several large projects (including a 'commercial' spacesim), and am hoping to gain some experience here.
tha_rami - the best way to predict the future is to invent it