Custom icon?

[shan]

Hey guys, i recently modified 4images and added a new extension to the list. Now when i upload a file with that extension, theres no image to display it. How can i tell 4images to show " custom icon" that i made specifically for that extension whenever a user uploads? Just like it would do with Jpeg or any other extension. I know this is probably the most easiest but im fairly new at this:(, please someone help...