You should definitely consider SharePoint 2003 rather than SPS2001.
Checkout
www.microsoft.com/.../wss.mspx.

In the portal, do users need a "read-only" view of the million pictures?
...or are do they also need to checkout/edit/checkin the pictures as well?

Where are the pictures stored today? ...a single Windows file system folder?
...rich hierarchy of file system folders?

What sort of metadata is needed to organize and search the documents? Are
all the pictures of the same "kind"? ...i.e. they have the same metadata
list of properties?

...there is lots to consider. Feel free to email me directly.