Am I missing something, or is the ability to go to the next image by pressing the corresponding arrow key on your keyboard not present? Assuming it isn't, this should be something quick to implement that I know my (and others') users would very much appreciate.
I love having Event RSVP'ing, as well as the new option of allowing users to un-RSVP themselves.
What I'd like to see implemented is a limit on how many members can RSVP. For example, allow an event creator to specify the maximum number of attendees that can RSVP when they create the event, and disallow further RSVPs once that threshold has been reached. Most events can't support an unlimited number of people, especially if your members actually actively use the feature, although having a 'Enter 0 for no limit' option would be important if this were added.
At present, if you force members to log in before accessing the website, the ability to use Calendar RSS/iCal exporting is broken. There should be an option that lets you select groups which can use these functions (with authentication, like I think Google's does), or at the very least override the security permissions (e.g. public to anyone who has the link). Either would be better than the way it is now.