One suggestion for the buttons: Don't use circle buttons, but make the shape of the buttons represent their function (i.e. a triangle for the play button, etc..) - this way, the buttons are easier to recognize, right now, people see "a bunch of circles" and then have to look at each one of them to parse their image.

Maybe you just want to remove the "button" background for each shape altogether and make the shapes just bigger, much like the built-in media player.