Here is my contribution for iTunes 11 skinning.
.i tried to make it as minimal as possible but it also still a work in progress so give it a try and tell me what u think i should add ,remove ,etc...
.changed a couple of things like (No Cover Art image).
.made some tiny fixes/changes.
.different preview to have better overall idea.
.updated to 11.0.2
.fixed a couple of misplaced scroll bars.
.updated to 11.1.5
.made many changes (less colors / more subtle).
.changed most of the original icons as it confuses me most of the time.
.to install simply replace the iTunes.rsrc in (Applications\iTunes.app\Contents\Resources) with the theme file.
but i only wish if it was green instead of red