I'll try to make it more clear.
All my posts have a jpeg image file, 418 pixels wide, uploaded from my hard drive. Let's call that the "small image". I would like visitors to be able to mouse over the "small image" on the post and click on it to be directed to a page on my server. This page on my server contains a 1024 pixels wide "large image", some text, and a button which directs the viewer back to the blog post.
If you go to http://blogbisogno.wordpress.com, you'll see what I mean. Each post has the text, "view larger image" under the photo, which is a link to the "large image" page I am talking about.
Example: The latest (top) post on my blog has a link going to the url, http://www.fotografia-la.com/html_pages/carrizo_pano_blog_large.html.
I want to keep that link and also add the capability of clicking on the "small image" to get to the "large image" page ( http://www.fotografia-la.com/html_pages/carrizo_pano_blog_large.html).