To remove Fantastico backups:
rm -rfv /home/*/fantastico_backups

Delete old Softaculous backups:

rm -f /home/*/softaculous_backups/backupname

You can also disable the automated backup from the  Softaculous setting

Delete cPanel File Manager temp files

File Manager always creates a temp file that may or may not get removed based on upload. You can remove the temp files using the following commands:

rm -fv /home/*/tmp/Cpanel_*

Remove cPanel update archives

/usr/local/apache.backup*
/home/cpeasyapache (actual name may vary depending on cpanel version)

Clean up Yum files

Every time you update yum it leaves package cache files on the server. You can use the following command to remove the yum files:

yum clean all

Remove unneeded accounts

You can check the cPanel accounts that hasn’t been used for long days. You can also check the suspended accounts from WHM >> Suspended accounts.

You can terminate the accounts WHM > Terminate an Account