You can use the following workaround only if the image is uploaded in a different external site. To do this, please follow the steps given below:

• Click the Settings tab.
• Click the Signature sub-link under Email Settings. This opens the Signature Settings page.
• Add the following code in a place where you wish to display the image :
  • <img src="http://<yourimageurl>" alt="photo">
  • Example : <img src="http://www.zoho.com/invoice/help/images/ZILogo.gif" alt="photo">
• Click on Save button to effect the changes in all your outgoing mails.