Here’s a tip for those who want more customization with their Firefox interface. This tweak allows you to use a custom background image for your toolbars.

• Pick an image in GIF format (it must be)
• Place it in the same directory as the userChrome.css
• Open your userChrome.css (Here’s how)
• Insert this code at the bottom
  /*Use a custom background image for the toolbars:*/
menubar, toolbox, toolbar, .tabbrowser-tabs {background-image: url("background.gif") !important;background-color: none !important;}
• Save the file
• Restart Firefox