Do you mean
this aurora? I've seen both versions in the game and both looks awesome, though I'm partial to the blue/green one myself and I haven't seen the other one with a clear sky yet. By the way I'm running on ultra settings at the moment, but I don't know at what quality steam takes the pictures.
There are already several mods that make the world look better, I tried one of them for a while but then I had to re install the game(no idea if it was because of the mod) and I haven't gotten around to installing it again.
The ghost ride was just something I came upon while out riding on the tundra west of Whiterun during the night. I've seen it twice and I still have no idea what it is. Figured I should follow it this time and see if it took me somewhere, but no such luck.