50 is the largest page size available in the ui.You would have to edit the source to change that. You can that fairly easily do so by editing the following files: /include/staff/profile.inc.php line 138./include/staff/settings-system.inc.php line 71.That being said I've never actually tried to do this, but I do not see any reason why increasing the number a bit would cause any problems. I would warn against making it display all... that could be horrible intensive on your database server if you have a ton of tickets. Also note that if you change this, when you upgrade oyour change will go away.