Aeon Small has an opaque background so you can see what you are doing. The roots of this theme reach back to the early days of Phoenix, which became Firebird, which became Firefox.
To get a more human-sized font, use the Theme Font & Size Changer extension. It makes life so much easier! Aeon Small is the same as Aeon, but uses the smaller icon set. Related themes include Aeon, Aeon Clouds, Aeon Colors, Aeon Big, and Aeon Jumbo. You might also enjoy one of the Scribblies themes, and Halloween.
Want to pick it up? Check it out on the Firefox Add-ons website.