Airtable does not publish a list of IP Addresses that you can whitelist, quite possibly because their IP Addresses are continually changing.
Your 2 solutions for this would be:
1. Move your photos to a URL that is publicly accessible by using a cloud drive provider like Google Drive, Dropbox, Box, Cloudinary, etc. There are many other providers as well.
2. Otherwise, if you'd like to keep your photos with your web hosting provider behind their firewall, you would need to use Make to move your photos from your web hosting provider's site to Airtable, because Make publishes their list of IP Addresses that you can whitelist.
There is a small learning curve with Make, which is why I created this basic navigation video to help. I also provide the links to a few other Make training resources there as well.
p.s. If you have a budget for your project and you’d like to hire an expert Airtable consultant to help you with any of this, please feel free to contact me through my website: Airtable consulting — ScottWorld