You don't need to set height and width anymore.
Make sure what you're entering in the URL field starts with "http" and ends with ".pgn", ".jpg" or ".gif". Not "[img]" and "[/img]" (that always messes me up!). Where are you hosting your image? Sometimes the URL the hosting site gives doesn't work right and you need to rightclick the image and get the URL there. If you're still having trouble and you want to post your image here, we can take a look and see if we can figure out the URL for you.