Hello @amava,
To let the user add an image, you can add the File upload field and then customize it to limit the size of the file and file type too. Here are the step by step instructions to the same:
https://premium.wpmudev.org/docs/wpmu-dev-plugins/forminator/#file-upload-field
About the image to be uploaded inside a square and being shown before submission, I’m afraid it is currently not possible to have the image being shown in a specific area on the form. We do have similar features requests and the same has been already passed on the forminator team.
Should you have any doubts or need any help, please feel free to reply back in the thread here and we would be happy to help.
Thank you,
Prathamesh Palve