WAS, it's simple. Old nebulae are the result of painstaking design in Photoshop of one or two basic TG renders, and a large number of small parts other renders. But the last nebulae are almost raw renderings. And in fact I'm flattered that you compare them, because I spent about 1-2 days to collect the old nebulae in Photoshop, and now for new nebulae it takes about 2-3 hours for post-processing (original images size 2048x2048 px).
I will remind you that for the game these new renders I will also cut into pieces and delete unsuccessful places, add stars, add beautiful gas streams and other things. However, this nebulae will be darker, as they will go to the background in the game scene. Therefore, while they are still bright and contrasting, I decided to show them to you. I hope I was able to clarify the situation.