Hi Jewel,
I have no idea and would be interested in finding out as well.
I did a search and found this in the forums:
https://www.etsy.com/teams/7718/questions/discuss/17908799/"If you go to leave a review for one of your purchases using the Etsy app on your phone, you will see a camera icon/button (below the stars) which you can click to attach a picture from your phone."
I am not sure, but it seems that you need to use your phone to be able to attach a picture to a review.
I would love to see responses from other Team members.