Actually i believe i did something like this-- Bare with me
Lets say the theme i was using was called Purple yet in the FRONTPAGE template, all images are beeing linked to by something like errm {imageshome}/newreply.gif
I went into my admin control panel and scrolled down the left hand side too REPLACEMENTS and clicked ADD.
From the replacemt set option i chose PURPLE because thats the style i was using, in the code to find i placed {imageshome}, and on the code to insert, i typed in the link to the images for example----
Say my images were located at
http://www.blahblah.com/forum/images/purple
I would type in the code insert -- forum/images
Hopefully i didnt confuse you too much, and hopefully it works for you. If not let me know and ill have to help you further