Well, the filesystem gives you hierarchy and an RDBMS can give you the tagging you need. To start, I would mock this up with a CGI that has access to a predefined set of folders. You can get a quick tagging system going by making the md5sum of the file be the key in a single table sqlitedb and create entries like (md5sum,tag) each time a tag is applied to a file. there are a million good directory strategies, research them. For thumb presentation try mirroring the full size photos from the top of the tree like: root->photos and root->thumbs, so when someone clicks the thumb, just change the root. this is just a start but i think you'll see how easy it can be. the hardest part will be presentation. you might also want to look at INTERCHANGE, since it is good at cataloguing, you might get most of the functionality you need there.