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.
Unfortunately, there is not a way to set the size the images needs to have at the moment of uploading them, what you can do is only set the limit in the file size that can be uploaded, please check this guide to get more details about it: Changing-the-File-Upload-Size-Limit
If you want we could escalate this thread to our second level as a feature request, so our developers may evaluate this and if there are more users requesting this same feature then it may be implemented.