The palm rest reminded me of the Moon Knight. So I used him as my inspiration. If you don't know who he is, he's basically an ancient Egyptian demigod who fights crime.
When I saw the theme and the colors that were available, it made me think of the ancient Japanese process of Indigo dyeing, or Aizome. When paired with the custom wrist-rest it looks like an antique katana lying against an indigo hakama from the past.
I made an effort to design something suited to the worn, aged appearance of the custom palmrest, so I came up with this look to evoke the feel of a controller for some sort of old, heavy construction equipment.