Not sure if this is possible but can i put one transparent image over the standard background image on the website.
body { font-family: Arial, Helvetic
Just add another url after a coma and it should work.
background: url('/images/body-bg.gif'), url('/images/anotherImage.png'); background-repeat: repeat-x;
You can find more info here.
UPDATE
You can find working example here, on jsfiddle. Sorry for the images, random gif and png from google.