How to make high quality skydomes?

Beautfiul skies can make a huge difference for games and are pretty low cost. I know about using nomipmap when I apply a texture to my skydome but still the graphic is not even close to something others do.

How? Games like destiny have stunning skies and I have some artists who can do these sort of textures but how do you put them up in UE4 that they look like that?

I did see the skybox tutorials and I can set up a regular skybox but how about setting up a high quality sky?