Hey, i recently wanted to try out a few mods for Civ4 but the mods i tried so far weren`t showing their custom backgrounds in the main menu.
I downloaded Caveman2Cosmos and Realism Invictus and even though the BGM changes, the background isn't.

Any ideas why? is that problem related to windows 10 maybe?

Civ 4 has a number of Problems with Win 10, with newer Hardware and old Hardware starting with patch 2.08, even worse for the nongogversion.
Depending at the system and the mods you're running it can be a maze of problems :)

On the bright side..there's a huge number of Fansites/mods/commpatches...


https://www.civforum.de/forumdisplay.php?177-Civ4-Modifikationen-und-Downloads

https://www.civ-wiki.de/wiki/Hauptseite

this german fansite is still active and during the past they where quite helpfull to me, hope you find something usefull there.