custom compiling packages?

[haVok]

this all started when I decided the lock screen icon in xscreensaver just plain sucked, so i used the ebuild command to unpack and compile it, while in between i swapped out the icons. Then I got the idea to do this with firefox too. I started with just changing the images in firefox for the preferences dialog, made new icons, same file type, size, etc. and replaced them in the unpacked source under browser,themes,linux, but to my surprise it did nothing the same ol' icons were back, this worked for xscreensaver, but so far not firefox, any ideas?