I recently bought a Wii U and everything works fine with the U software, however when I switch to the standard Wii menu, I am met with a black border around my screen and a very low quality image.
I have my Wii Us resolution settings at 1080p, I've tried it at 420p too. It doesn't seem to affect the emulators image. I looked for a graphics setting area on the Wii emu, but I couldn't find anything.