Interface changes = crash.

Here, I'm attaching a link to the UserInterface files used in the mod.

So, to report: I couldn't reproduce the crashes. Perhaps the files you sent weren't the right ones, because in the lobby for creating a multiplayer game (where the video showed a long loading time), the button you added is missing.
I noticed other errors:
- In the file [InfoWindows\Buttons\CreatureInfo\Conjunction\InfoB utton.(BackgroundSimpleTexture).xdb], the ClassTypeID is incorrect.
- Many dds files intended for the interface use mipmaps, which is very bad because when the graphics level is changed to below high, the game becomes unstable and crashes. (You need to abandon mipmaps in the interface textures, and where mipmaps are necessary, generate them in multiples of 4, as in the original game files).

Since I couldn't reproduce the error, I assume that the path to the working folder in the shortcut may have changed (I had a similar issue, and the game behaves unstably - it crashes at the beginning). Try launching the game without using the shortcut.
Also, don't forget about the d3d9.dll file, which may also have an impact