Background image current menu item

How can you set the background image for the current menu item?

I tried doing stuff like:
.current-menu-item:first-child>a:before, .current-menu-item:first-child>a:after {}
but no matter what I do the ‘current’ image falls behind the ‘passive’ image. (z-index is at 99999999999999999999 or something)

Not sure if it would matter but the background image is a sprite.

You can see the menu at hookahi.com, its the main one. Right now the tab all the way to the right ‘contact us’ is the only one with the tested code. (also a side note, I am not sure why, but for some reason when I put my menu to the right all the menu items are backwards, as in the one all the way to the right is first child and the one all the way to the left is last child).