I whipped up an AppleScript for iChatStatus to set your iChat icon to the album art for the currently playing song. It’s an amalgam of the default iTunes script for iChatStatus and a script that sets the iChat icon. I haven’t tested it too throughly, but it seems to be working for me.
In addition to iChatStatus, you’ll need GraphicsImporter OSAX installed, since that’s what the iChat icon script I assimilated used. Download iCS Album Art.scpt or copy and paste the code in this entry into Script Editor.
If you need help getting album art for your music, I’ve had a lot of success with Find Album Artwork With Google.