> I think you missed a "click". Once you click on the thumbnail it takes you to that product's page. Then click on the picture again and you get a very large picture with clear details.

Nope, that wasn't what I missed. I checked again, on different pages, and found suitably large images. I think it was just the pages I was looking at. This one, for example:

http://madebytess.com/oneofkind.html

...has pretty tiny "large" versions. So I guess the issue is that just some of the products don't have suitably large images for them.

The other thing that's weird is that on pages like:

http://madebytess.com/notionsbags2.html

...you can click on the product images to get a blow-up version, but you can also click on the header image at the top and get a...small version. It seems strange that these header images would link to anything at all.

But I also second the suggestion to put an explicit "click for a larger version" note somewhere.