Hey mate, how is the website project going so far? Anything still giving you trouble? I've been putting together WP sites and morphing them to client satisfaction for a few years now so I may be of some help to ya.
The thumbnail plug in you are referring to is called "Lightbox". If you can't find it let me know.
However, several themes on Mojo Themes have that feature already built in. I've bought all my themes (with one exception) from that site. Versatile, affordable and free updates for life
Let me know if there's anything I can do to help out!
Good luck!
Some examples of sites I've put together:
http://thebestguitarlessons.com (my business)
http://www.devendecoste.com (portfolio site)
And I'm guessing this is what you're trying to accomplish with the images?
http://www.devendecoste.com/how-stretch-a-silk-screen/
Mind you I don't code them but do know enough HTML/CSS to play with the custom styles of themes.