Recently Google announced that GMail will now support images as part of e-mail signatures. Here is how you set it up.
1. Click on the Settings page of your GMail account.
2. Click on the rich text editor in the signature. In the rich text editor, you will notice that there is a way to add formatting, links, and images.
3. GMail now lets you support a unique signature for each e-mail address that is associated with your account. You can edit the signature for each account by changing the e-mail address in the drop-down box.