Just activated this on 1.7.4. The other back to top started giving jquery errors. I like being able to change the back to top image, and no errors. If you want to add an custom image. i found the good size is 40px by 40px. Just upload it to your image files for the plugin, and change the image in the css files. Remember to enable dev mode, and go to your site and refresh. Then disable dev mode.