Here is a mod I did last year for a customer.
It started out as a quick one week build but I begged him to let me work some magic on it. He said I could do whatever I want. BIG MISTAKE! :P
I decided to just paint the inside of the case first. But then I thought I could experiment. So I used some rubberized undercoating instead of paint. My idea was that it would cut way down on sound. It does! It's so quiet you can barely tell it's on.
Then it took on a life of it's own. I did some research and discovered that "conformal coating" can be used as a protective layer for electronics. AND, it can be top coated. So I decided to risk painting the mobo flat black. It worked with no problems!
There was a lot more to it but that's the short story.
Here's the pics.
Thanks for looking 8-)