I also have 41,5Mb PNG in 7677х5667 if someone's interesting
It was hell to screencap it screen by screen and then to put everything together and to clean everything...
But now that I think about it, wouldn't it be much, much easier to just rip the game's textures? Most Wii games feature files in the same format, especially if they were coded with the main Wii Dev Kit. If yet the texture ripping turns out to be impratical, there is also the possibility of texture dumping, by running the game on Dolphin, putting the map on the screen and using the texture dumping option of the emulator (or by using 3DRipper) to dump the current textures loaded into the VRAM. It would save us from the trouble of lookig for filenames in order to find the texture files for the map, since I assume the city map uses multiple 512x512 textures.