So in this post, I'll write all my discoveries 'bout Wii U Menu
Location:
storage_mlc/sys/title/00050010/10040200 (EU)
storage_mlc/sys/title/00050010/10040100 (USA)
"Directories"
meta/
iconTex.tga - An icon with the Wii U Logo, not used though
bootTvTex.tga - Black, not used...