I'm glad you brought this up, because this was a problem I was having during development. Before the first beta release, there was no fog and the map was relatively sunny, so I had rolling hills in the background with a few other skybox props. It was at a later point I added the fog, but I kept the original skybox for the beta 1 release (which you can see in the screenshot at the end of this post).
The only problem was that with the fog, you get that "silhouette" effect, no matter what distance it is from the viewers eye. When I started development on the beta 2 version and changed a few visual aspects, I felt that effect got even more distracting. My solution was to drop all the rolling hills to bring the skybox somewhat level with the map. Right now I believe the fog is set to begin at 300 and end at 4000, which seems to be pretty reasonable. I believe I kept the same settings for the skybox fog as well. The fog made things trickier for sure, if there are any suggestions on how to properly handle fog with the skybox, I'd love to hear them.