The official page of signature templates can be found here. You can also find templates that have been submitted by users in this forum.

Submitting Signature Templates:

If you would like to submit a signature template, simply create a new topic in this forum with a subject that best describes your template. If there are enough people that like it, your template could be included on the official signature page. Be sure to provide the HTML you used in your template and try to follow the format below.

Sample Template Submission Post

Try reducing the size of the HTML and changing the font color of the parts that need to be customized in red. You can also paste your signature as it will appear by copying and pasting the result from Gmail.