Can you run it from the terminal:

And give me the output?

Changing the background to black isn't as easy as changing the png. I messed with the background colors once because I agree, black looks better, but it caused readability issues with the popup boxes and prompts and stuff so I keep the 'system' default. I don't set the background color at all and on Diablo it sets it to white and on Fremantle it sets it to black. This way the popups and text are all readable.