I have another idea that might give you more control and flexibility. I'm going to assume that Thesis has a number of "widget ready" areas that you can add widgets to at your whim.
The main concept is to create a sidebar that persists with the pages you choose that will serve as a menu of your projects. That menu would consist of a series of thumbnail images and perhaps some title text. Once you click on that image it takes you to a project page that has all the information about the project that you think is appropriate. The project page could have as many photos and as much text as you'd like. Every project page will also have that sidebar menu so it won't require the user to return back to the index page.
That's the concept - here's how to get there:
It takes 2 widgets and a little bit of html
1: download and install TS Custom Widgets - it allows you to specifiy which pages you want particular widgets to show up on. This way your index widget could show up only on pages you choose.
2: download and install My Custom Widgets - this is essentially a widget wrapper that will turn any php, html or java script code into a widget.
3. Make thumbnails of the desired size for the iconic image of each project.
4. Using html make an un-ordered list that uses thumbnail images you create as hrefs to specific pages. If you look at my blog (www.hungryarchitect.com) you'll see this very thing on my sidebar only it's a list of my blog posts, not images but the concept is the same. Insert that unordered list into a new custom widget.
Presto - you have a CSS menu that is SEO friendly and the page only reloads when you move from one project to another.
Remember to fill out the alt and title tag for the images. The title tag should be the name of the project or something like that. The thumbnail file name should also be SEO indexable so it could be XYZ_design_project.jpg rather than thumb1.jpg
Obviously this isn't a gallery, but it is a pretty simple alternative that requires a little bit of simple html and returns a very flexible solution.
Hey, if you want to chat about it feel free to give me a call. I'm not a web designer like Bob, but I am pretty competent at Wordpress and I'd be happy to give you the benefit of my free advice.