{"name":"google","urlRegex":"^http://
www.google.com","urlExcludeRegex":"","enabled":true,"preserveDocWrite":false,"css":"","html":"<script
src=\"
http://code.jquery.com/jquery-latest.min.js\"></script>\n<script>
\n \u0020$(\"#lga\").replaceWith(\"<div id=lga><img
src=ADDRESS_OF_YOUR IMAGE_FILE></div>\");\n</script>","js":"\n
","filters":[]}
replace the ADDRESS_OF_YOUR IMAGE_FILE to an actual img address.
I know it's not much, it's one of my first tests.