When you say that there is no URL for the inserted picture, is the picture within your Library? Are you trying to make the image a clickable link? Are you getting a particular error message when you are trying to add a picture?
If you are adding an image via URL, some things that might help are to ensure that the url ends in .jpg, .png or .gif. Also make sure to include the full url starting with http://.
If you are still getting an error can you please reply with how you are trying to insert the image (via your library or via URL) and the text of any error message that you may be getting?