Finally, by a chance I have found out like one introduces a picture in the Mainmenu and would like to present to you here the result. Indeed, I also wanted to substitute for Sion with another person, however, this did not succeed, thus only this picture of the Polcaps of Telos as a background picture in the Mainmenu as a Mod is available.
Bugs: I hope none.
Installation: Simply tga in the Override copy.
Deinstallation: Tga simply delete from the Override.
Disclaimer: This Mod is my idea.
I hope you have an crowd of fun with this Mod.
Here the Picture:
and here the Link to the Mod: