Link Icons (and how to change them)

[Casimir]

I've been trying to alter the link icons in an extension I'm working on from the default (the little red or green square with the white dragon image) to a custom icon graphic. I've attempted to do this via methods I've seen in other extensions by adding the <icon> code to my extension, but this hasn't worked so far. What I currently have is the extension.xml and a graphics_icon.xml - I've placed the following code into the graphics_icon.xml and ensured it is included / linked in the extension.xml:

<?xml version="1.0" encoding="iso-8859-1"?>
<root>
     <icon name="button_link_down" file="graphics/buttons/button_link_down.png" />
</root>

This unfortunately hasn't changed the icon. I'm thinking it could be possible I need to place the <icon> tag in a different file maybe?

EDIT: I forgot to mention this is using Unity and CoreRPG as the base.

[Trenloe]

The "button_link_down" icon is used when the link button is pressed. You also need to define "button_link"

[Casimir]

Always the little things. For some reason that didn't even occur to me. Thanks a lot Trenloe.