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.
Do you mean background image? To change background image's size, you can check the thread: How to change the size of background image using the Form Designer. If I didn't get what you mean, can you provide more details in your query so we can help?
Do let us know if you need further assistance.