this is exactly the type of thing you would build a facebook application for, though. if the Page uses a tab, when someone clicks the application tab on their profile, facebook requests a page on your server and just puts it in the tab.
so, while you still wouldn't be able to use JS on the tab load, because it was just requested from your server, it could show the last few images on their account.
Yeah this is the best solution I've found for putting dynamic content on a Facebook Fan Page. It requires a custom solution but I'd like to eventually build an app that allows anyone to add a custom/dynamic tab to their fan page.
so, while you still wouldn't be able to use JS on the tab load, because it was just requested from your server, it could show the last few images on their account.