I have been want to to do this too. I have got the pictures on imagestation and i found the URL. Its a zillion characters long. how do you cut and paste it?
When your looking at the pic at Imagestation in full screen mode, right click on the pic then choose copy.
When you come back here, then right click to paste it in the signature box (if you want it part of your signature) located in the User CP. Remember to add [ IMG ] Imagestation pic address [ /IMG ] tags.
If you just want to stick a pic into a post, then you can use the IMG button.