When this plugin option is checked, is the code added to the pages album/index/image.php or must it be done manually? i checked it but cannot trace "printUserLogout" in the source code.

It must be done manually. place `` wherever you want this link/form to appear.

So, what does the plugin do?

I added the code, it prints a text "logout". But, I thought it would only appear when the guest from the Gallery Config page signs in. I see it when in Admin.

It shows whenever anyone is logged in. If no one is logged in the login form will show.

Is there modification to the syntax that would allow an image to be used for logout?

You can do this yourself. The link is href="?userlog=0"

I substitute the print... for the href... but where is the name of the image included?

You need to learn some more about HTML if you are going to make this sort of modification. The normal way to do this is ``

Know HMTL, wasn't sure how the PHP code fitted in