Adding logo and hyperlinking

See the great post by Zeehond here...

http://thumped.com/bbs/showthread.php?67266-How-to-make-clickable-link-from-and- image-in-mac-mail

To insert a link in your Mac OS X Mail signature:

Type the URL.
Mac OS X Mail automatically creates links for all web site addresses starting with "http://" or "www".
To link text or an image in a Mac OS X Mail signature:

Click in the signature you want to edit in Mail preferences' Signatures tab.
Press Command-A.
Now press Command-C.
Press Command-N to create a new message.
Click in the message body.
Press Command-A again.
Press Command-V.
Highlight the text or image you want to link.
Select Edit | Link | Add... from the menu.
Enter the desired address.
Click OK.
Press Command-A once more to highlight all text.
Press Command-C.
Go back to the Signatures preferences window.
Make sure the entire signature text is still highlighted.
If it is not, click in the signature and press, yes, Command-A.
Press Command-V.
Close the Signatures window.
Close the New Message window as well, not saving the email as a draft.
Note that such rich-text links will not be present in the plain-text equivalent Mac OS X Mail automatically generates for recipients who prefer to read their mail in just text.

Or fancier...

http://smokingapples.com/miscellaneous/html-signature-apple-mail/

iirc, I think somebody in the replies did it in Mail 2.1.3 there after a couple of tries.