Another idea would be to add an option “help” popup/tooltip for each item. Eg a ? that could be hovered over to show some additional information.
Also when a large file is submitted (larger than the max allowed) it takes ages to submit then comes back saying the form has been submitted… Well, the file is not attached to the email, as I assume it’s too large to upload. It would be good for an error message saying the file was too large to be shown, and even better, an error before submitting saying that the file is too large (not sure if the second is possible though). I know you can leave a message saying “files must be smaller than 100KB” or whatever but people don’t always listen.
And, this leads me to my final idea for the form creator (for now anyway)… To be able to set a maximum size for file uploads, which is validated and shown on the form.