I like the dirt look, you can really push it and make it more realistic.
I would make the play buttons as if they were ingraved in the metal (solid shape) and filled with dirt/rust so it has more contrast. Same for the logo behind the playlist.
as for the shuffle/repeat and where to put it, where its at is ok with me, i think it should be close to the playbuttons no matter what. So you could either make them icons instead of text and or move it to the left side.
you could split the playlist from bottom (remove all text under where the current song is highlighted).
Then you can put buttons and stuff under that that goes to where ever.
some other ideas,
i would make those screws buttons, like the one above the vol i would make a mute or att button and make one of the states with teh screw unscrewed and hanging off to the side.
you could indent the middle area and make it a fake lcd screen with metal as the border, instead of a flat metal plate.