If you use something like WiiScrubber you can modify the contents of a disk image, but you'd have to know exactly how files are stored and you might be very limited as to what you can change, as there may not be any room for better textures.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56