Change number of items per admin page

Since a few versions WordPress has the option to change the number of items displayed per page. It is located under the screen options drop down tab. I have a gallery plugin (tn3 gallery) which doesn’t have this option and I just can’t force it to display more images per admin page than 20.

Is wordpress intentionally blocking plugins from using the ‘items per page’ function? Where should I hand-tweak a wordpress file to change the default number to 200 or more? I have tried numerous files from the wp-admin/includes directory but with no positive results.