Hello Sarah, 

> Any suggestion.

I would suggest then you have a good look at what exists already. From my 
own experiments, I know about a good 20 such applications, both native 
(Windows, Linux) and Web based. They are mostly free (or at very little 
charge) and provide you with proprietary databases that are optimized for 
photo storage, sometimes just using Mysql as a backend. 

What you describe is a rather big project (if entertaken seriously) and I 
don't see why you would launch yourself into such a thing when you can just 
download and install. 

Of course, if you are just looking for a project to start some serious Ruby 
programming with, this is it. You might want to sketch all of that down and 
start doing examples with all the libraries involved, so as to get a 'feel 
for the turf'. Ruby is a good language for such a task. 

best of luck, 
kaspar

hand manufactured code - www.tua.ch/ruby