To remove the email from showing on the frontend, edit file "Joomla Root/components/com_guestbook/views/guestbook/tmpl/default.php" around line 34 remove " '.$postlists->post_email.'');?>"

An option to show could be added to the admin end or to the post comment form so the user chooses very easy, maybe in the next release.

Also an option where to place the image, above text/below, e.t.c..

Allow multiple images and show in a lightbox in the comments single full view.

The component name does not appear to change the name in the frontend, i will take a look why in a bit.