I have my blog locked so you can't right click, but a friend of mine noted that when you click on the picture that is uploaded within Blogger, it takes it to another screen where you can then right click and download the picture. I believe I have fixed this issue. You shouldn't be able to click on the picture in this entry and enlarge it. It should be static.
Here is how I did it. The following is the code I see in the "Edit HTML" side of composing a blog entry.
I added the red to show you what I deleted (don't forget the last little red bit at the end). After you delete that code, go into the preview screen and try clicking on the photos. If you get a message asking you if you really want to navagate away from the page, you did something wrong. If nothing happens, you did it right. Also, if you see some wierd code by your pictures, or your picture didn't show up, you either didn't delete everything you should have, or you deleted too much.
Please try it and let me know what you think and if it works for you.
This is only for use when you are uploading your pictures within Blogger. If you are using "Edit HTML" and pulling code from a site like Flickr, you will need to change the settings within Flickr to not allow downloads. I have done this at my Flickr account.