There are no other changes made to the mainmenu. You won't notice a thing until you want to inject an image (8:8:8:8 ARGB/A8R8G8B8 224x207 DDS) for your preview image.
Thanks to:
-Aequitas for trying to teach me how to do this in hex.
-Iron_Forge/Serenity for providing me an easy way out.
-Farklem/DotHalo for letting me remove the map entries Serenity put in.
-low8/SPPF for making me a working patch.
-http://www.imageviper.com/ for hosting my images.
-WinRAR for turning a 7MB patch into 4KB.
Here's some proof, showing map image 49 pointing to its own offset and being plain white:
