How to add background img to current page link?

site: http://www.jakespharler.com
theme: child twenty-twelve

Problem: I want the current page I’m on to show an image/arrow next to the link that opens the page. So if I am on the ‘About’ page, then there should be an arrow next to the ‘About’ link in the nav menu.

My failed approach: I figured I needed a background image, so I tried inserting it using the following code:

#menu-item-252 a .current_page_item:link {
background-image: url(arrow img...);
background-repeat: no-repeat;
}

…I’ve also tried a several other approaches with no success 🙁

Thanks for your time!