Looks great. I'd love a way to view full resolution images without having to download it.
Out of curiosity why do you want to view the full-resolution photos vs. the ones that are scaled to fit your screen?
There's now a link next to the "Download Photo" button called "View Original" when you click to view the larger photos.
Update
Unfortunately on Chrome this link doesn't work because the photo is stored in a way that tells Chrome to automatically download the photo. I'll have to dig in to figure out if there is a way to force the photo to be displayed instead of automatically downloaded.
Overall, it looks great. My family would definitely use it, for similar reasons to yours. Nice work!
You want "Content-disposition: inline" or no content-disposition header.