That support article is for SMP (Altiris). Not relevant to DLP
Look here;
SymantecDLP/Protect/tomcat/webapps/ProtectManager/graphics/general
There you will find a file named DLPBannerEmail.gif
Replace it with one you prefer. You'll probably have to do some editing to the image to get it sized correctly (350 x 40).
Generate a report and email it to yourself.