This is "add-on" allows the administrator to change the pagination size of category, manufacturer and product pages in the administration area. It also allows to disable pagination.
Just download the files and replace. Compile.
Once compiled, the configuration is available at admin->configuration->Global Settings-> last tab
http://www.2shared.com/file/XcANhr6r/pagination_config.html
This could be improved by allowing to configure others pagination settings like localization or all settings.
It could also use some javascript to only show the page size text box if the allow check box is selected.
Hope this can help someone.