As far as I know, system messages are only shown on tty0, so you can use ALT-Fn to switch to other ttys and you won't get those messages. If you do not want to see the messages, I think you need to edit your syslog.conf (or syslog-ng.conf) and create an entry that redirects the messages to a file or elsewhere. Unfortunately I don't have much experience with sylogd, so can't be more precise.
Is there any way to turn off the messages that come up on screen from netfilter?
When I try to admin a machine with kernel messages coming up every 10 seconds it is very off putting.