As far as I know, Airtable’s automations do not support inline attachments of images. Airtable only allows attaching attachments as files to the bottom of the message.
However, you can very easily do this with Make’s automations. Check out the screenshot below for how the Gmail module would be configured in Make… it is pulling the large thumbnail image from an Airtable attachment field, and embedding it with the HTML <img src> tag in the body of the email.
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. For example, to instantly trigger your Make scenarios from Airtable, check out this thread. There are also many Make experts hanging out 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