What is the largest file size i can attach to a form? and would the format make a difference?

one of our team members was unable to attach a logo and the error message stated that the file was too big

With regards to the file size limit, I would suggest you check this guide:

https://www.jotform.com/help/33-Changing-the-File-Upload-Size-Limit

and as for the allowed file types, please check this one: https://www.jotform.com/help/29-How-to-Change-the-Allowed-File-Types-Extensions-in-the-Upload-Field

Then, if you have any further questions or if, in any case, I have misunderstood your concern, please do not hesitate to let us know.

Thank you.