Try this:
Go to Tools - Options - Mail Format - Signatures -
Choose edit on the signature you are working with and clck Advanced Edit -
(can alos be done when entering New signature)
This will open an editor (usually Word) and you can insert your graphics.
However, graphics will only show in rich format messages. If you are
replying to a text message the graphics will not show, just a white box.
hth
Gary