I've looked through documentation and the GUI without luck. Is there any means of creating a login (welcome) banner on the security manager prior to the login window?
NSM 184.108.40.206 has the log-on banner option which enables you to upload your company logo (or any other relevant image) and customized text on the Manager /Central Manager logon page.
There is no way to configure this on any previous release. Also note that 4.1 is EOL this year: