substitute
http://www.bragg.army.mil/AFVC-C/panthers.htm
for the path to the pic you want to use:
http://www.bragg.army.mil/AFVC-C/images/505dui.gif
http://www.bragg.army.mil/AFVC-C/images/Masatac.gif
http://www.bragg.army.mil/AFVC-C/images/crest.gif
or whatever
most of the sig files have been custom made - if you want me to do you one (this is not an open invitation to everyone) then pm me and we'll put our heads together.