Please run a quick script to ensure that all assets are available in the right places.
In the /wrongtown_goombanistan/ folder you will find a .bat file called 1 - Backup core game files and replace.bat. This will make a backup copy of existing core files (e.g. ..\mods\core_gfx\assets\gfx\Untitled-1.png will be copied to ..\mods\core_gfx\assets\gfx\Untitled-1.bak) and then replace those files with modified versions that support the complete Goombanistan experience.
If you would like to revert these changes, I've included 2 - Revert to backed up core game files.bat which will replace the amended files with their originals.