I have heard of customisation of Foobar2000, but I keep my computer minimalistic right now I'm back to Windows Classic for ease of reading but at times I skin it down even more.
On Neowin there is an entire topic dedicated to the customisation of Foobar, although recently Foobar released a new version of their player after weeks in beta to the public, and I am unsure wether this new version which GUI wise differes little to the old version is compatable.
The topic if you are interested is located
HERE