When products are uploaded using the cart product setup screen thumbnails are automatically generated by the cart. If you are importing your products the thumbnail images are not automatically generated and you will need to upload your thumbnail images. Here is a tip to quickly generate your thumbnail images all at once.
1. Download the Image Resizer PowerToy from Microsoft for your flavor of Windows.
2. Go to Portals/(Portal #)/SmithCart/Thumbnails
3. CTRL-A to select all files
4. Right-click on a file, select "Resize Image"