@M R L
its simple bro
Go to User Control Panel>Edit Profile>Edit Signature then
you can see your current signature in the form of text,,.
now place curser where u want to add Picture,,
\Click on Img Button on Top, it ll b like this a
and Copy image URL here <> [img]<>[/img]
Ur picture should not over 150 * 150 pixels
then click Ok