You can also grab the URL of a resort image right out of any post in which that image appears. Just "right click" on a resort image and in the menu that pops up, click on "Properties". Select the text (the URL) in the "Address" property and copy it (hold down the Control key and press the "c" key).
When you edit your signature, paste that URL into the image tag (to paste: hold down the Control key and press the "v" key).