There are two files in cPanel that will help to exclude files or accounts from cpbackups.
To exclude a user in the server from cPanel backup, add the user to the file:
/etc/cpbackup-userskip.conf
To exclude a file from backup, add that file to exclude path to the cPanel file:
/etc/cpbackup-exclude.conf
Restart cpanel
/etc/init.d/cpanel restart