What are thumbnails?
In Photoshop Elements you need to install two files, the action (.atn) file and a corresponding thumbnail (.psd in PSE5 and .png in PSE6-PSE8). The thumbnail is a tiny 64px by 64px image file that will load in your action pane in PSE. This is the image you will click on to start the action. The thumbnail name has to be identical to the action name or they won’t work! My action did not come with a thumbnail and I have PSE. No problem! You don’t need a thumbnail file for the action to work, but instead of an image in your action pane you will see a gray square. Just dangle your mouse over the square to see which action it goes with. If you want to make a thumbnail just create a 64px by 64px square and put text/image to taste. Flatten it and save it as a .psd (if you have PSE5) or .png (if you have PSE6-PSE8). Make sure to name it the exact same name as the action or it won’t work.
Thumbnail has to be the most misunderstood term on the Internet. The best way to define it is to tell you what a Thumbnail is and what a Thumbnail is not. What Thumbnails are: A thumbnail is a collection of pictures all put into one picture, sort of an index of a picture set. However, on the web, this definition has been extended a bit. Because a large thumbnail picture often takes a while to load up on the web, most websites think of thumbnails as smaller versions of the full size pictures. These smaller versions are used in a web gallery page as a preview to the full size pictures. The Thumbnails are used as links to the full-sized, original picture. This allows visitors to browse through the picture gallery faster and save whatever pictures they like without having to wait for all the full-sized versions of the pictures to download. What Thumbnails are not: Thumbnails are not full-size pictures resized on the gallery page by using the width and height properties in the IMG tag. Pict
