How do u replace generic folder icons?

Hi all.
I have successfully added poster art for my movies using Sapphire. However, there are still lots of generic “S” icons (pic with an “S” in it) that are displayed when navigating thru folders. Is there a way to replace these generic pictures/icons with ones that I specially create (e.g., using Photoshop)?
In case it makes any difference regarding the answer, I have not upgraded my atvflash or AppleTV to the lastest versions because I don’t like the new AppleTV interface.