8 steps to - Gmail rich text signature ... here is how to.

1- Go to https://mail.google.com/mail/?shva=1#settings

2- Click on the Signature field and if you have a logo (save on Flickr or other photos site)
3- Place the cursor where you want the logo to appear, then click on the 'picture' icon on the text editor toolbar.
4- Go to Flickr or other photo site where you have your logo saved online.
5- Right click on photo/logo (PC) or 'Control + Click' on Mac to copy the 'Image Location'
Screen_shot_2010-07-08_at_8
6- Go back to Gmail / Signature settings tab.
7- Paste the 'Image Location' URL in the URL field.
8- Save. You're done.

see below for result.
 

-- 
Yann Ropars
Partner

Extanz.com - Social Media Marketing and PR 2.0
http://extanz.com

Sterena.com - Health communication meets the participatory web.
http://sterena.com

Fort Collins, CO