OMMaps is a mod released under Old Memories line that restores map loading screen backgrounds that were used before update 1.0/0.9.23.
A mod that is easy to maintain and immune to game updates. It does not contain Python or Scaleform elements because if you want to replace one image with another, just... name the image you want to see the same way as the original! The mod uses 0.9.22.0.1 game client's resources but in some cases it has to pick up even older resources, for example, Berlin's assets were taken from 0.9.13 game client.
You can compare the mod with generic diff patch that is used, for example, by Wargaming.net Game Center to update your game. If the image exists in OMMaps package, it will be used then. The mod has assets for Prokhorovka map so it will use them while Studzianki was never seen by anyone before update 1.0, (supertesters, remain silent!) so game client resources will be used instead.