I see that this reply is about 1 year old now, and LMS is now up to version 3.2.

An example of customers that this would help would be the US Department of Defense. They are required to use a standardized warning banner on all systems.

Even a customized message of the day (MOTD) area would be a great improvement.

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Does this answer still apply to LMS 3.2? Is there still no ability to customize the login screen in any manner?

Nothing has changed in LMS with regard to this feature.

an undocumented feature of LMS might help you in this case. I found it while digging in the filesystem of NMSROOT.

make a backup of the following file then open it in a text editor:
NMSROOT\lib\classpath\cscommon.properties
enter the message between the double quotes of the parameter CUSTOM_LOGIN_MESSAGE. It should looks like this:

CUSTOM_LOGIN_MESSAGE="your message for everyone who login to LMS"

Save the file and be careful that you DO NOT CHANGE the file extension!
No reboot required.
Now, everyone that successfully login to LMS gets a pop-up with this message.