What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I see that you have already added a log in your form. Anyways, to answer your question, yes it is possible, you could try adding a cover image instead. Please see our guide here: http://www.jotform.com/help/75-Customize-your-Form-using-Custom-CSS-Codes.
Or you could use the image field found under the Form Tools.
It's easier to use this so that you could position the image more appropriately instead of using CSS code, although, you could also use that instead.