No, Beulah, entering data, including uploading of graphic items, is limited to members. Could you imagine if everyone in the world had unlimited ability to edit WikiTree profiles?
There is no reason why your grandson cannot join WikiTree so that he will be able to upload pictures to family profiles. He doesn't ever have to participate in any way and, if he feels that strongly about it, he can even close his account after he is done adding the pictures.
EDITED TO ADD: I just saw Melanie's generous offer to help. If you or your grandson would like to email the pictures, along with which profiles you want each one on, to either Melanie or me, one of us could add them as long as the profiles are open or if you add one of us to the trusted list just long enough to do it.