Background info: 2 semesters of C#(WinForms), plenty of HTML/CSS skill, brand new to asp.net.

I'm building a site for a friend who's a photographer. It's just a gallery site, but he'd like to be able to update the galleries himself and he's not tech savvy in the least. So I'm using the following approach to the problem:

Using ASP.NET 4 WebForms:

I'm using System.IO to get the names of the folders which represent the "Galleries" and populating a TreeView control for navigation.

When a "Gallery" is selected, I have code that builds a (HTML)list of the image files and populates an UpdatePanel with this list.

As this is all based on the folders/files, I'm building him an secure admin page to upload files to new or existing galleries(folders). He'll also be able to edit(move/delete) the existing files from there. 

I got it all to work, which was a nice little victory, but I'm realizing this approach is not optimal, as none of the unique galleries are findable via search engine or even URL; the SEO value is nill; the browser back/forward buttons are useless...

Can you guys/gals recommend a better way to go about this? 
Is there a way to modify what I've already done to optimize the project?

I'll gladly start over to do this right.

Thanks