The Atom CPU is quite nippy for what it is, and for a server its more than adequate. I ran a web server on a 166MHz Pentium I once!!! Ran a little slow but it was usable
The bigger the HD you can get the better obviously, since a server is supposed to have more storage than normal.
Also remember to backup those photos. Don't rely on a single hard disk to keep them forever. I did that once and I almost regret it. Thankfully it came back to life long enough to get the valuable photos off.