Newly uploaded photos

Well, first of all - very interesting website... Hopefully you guyz get lots of users so everybody can help out eachother... Back to my topic.

I have a photo gallery where user can upload photos. I'm using ImageUploader therefore datestamps for each photo uploaded vary between 20sec-2min depending on users connection. User can upload up to 50 photos at once therefore the first photo that gets uploaded has a date stamp of eg. Jan 01 2008 12:00:00 and the last photo uploaded in that session will have a date stamp of Jan 01 2008 12:10:00 which is 10 mins after the first photo.

My question is how do I query the database to get newly added photos. I was thinking of grouping photos that are 1hr or more apart from eachother and generating an average datestamp for those photos (or just use the last photos datestamp). How would I go about doing that using one or more queries in MySQL and maybe with the help of PHP too.

Thank You,