Crossfire Modding Guide
Modding Crossfire is fast and easy, changing your ingame kill icons (and many other icons), the log-in screen, music, the interface, and many other things can be done by simply replacing the corresponding file.
Unless you opted to change the installation directory modable files will be located in:
C:\Program Files\Z8Games\CrossFire\rez\
or
C:\Program Files\SubaGames\CrossFire\rez\
depending on which website you downloaded the game from. (If you downloaded it from a third party site, check for both.)
Rather then explaining what everything is in a block of text, I figured this would be simpler, most of it is self explanatory, I've just highlighted the most often modded things.
Make sure that you rename your file of choice the name of whatever you're replacing exactly to the letter, it also must be of the same file type.
That's all there is to it!