Accepted Solutions (1)
Great question and I am very interested in this as well. Prior to BIMI, I had asked my account team how I can get my brand profile image in Gmail, as I have seen a few (but not many) brands do it. Their response is below, in case this is of interest. But if anyone has any experience with BIMI for this purpose I would like to know 
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There is no "programmatic" way to affect the profile picture (for Gmail).
The best way to apply a profile picture to Gmail recipients' inboxes is to create a Google+ account for the sending address and add a profile picture to it (more below)
Other email services and inboxes (including Airmail, Sparrow, Postbox, and Thunderbird) use Gravatar (more below)
Use Google+ to add profile pics to Gmail:
• Go to http://plus.google.com/
• If you are already logged in, log out
• Click "Use another account"
• Click "More options" -> "Create account"
• Enter first and last name
• Under Choose your username click "I prefer to use my current email address"
• Enter the email address you want to send from with a profile picture to the "Your email address" field
• Fill out the rest of the fields
• Once your account is created, click your profile in the top right, and click "Change: where your profile picture should be. Upload a profile picture
• Now wait for a day or two
• Profile will be updated
Use Gravatar to add profile pics to other inboxes:
• Go to http://gravatar.com/
• Click Sign In and sign in if you are not already
• Add an email address - use the email address to want to send form with a profile picture
• Upload an image
Some more information :
https://litmus.com/community/discussions/6683-sender-image
https://stackoverflow.com/questions/43091844/send-email-with-profile-picture-php-mail-function
https://litmus.com/community/discussions/6683-sender-image
https://productforums.google.com/forum/#!msg/gmail/nR3E3d3aHVY/WH_RmYUxAQAJ
https://www.labnol.org/internet/email-senders-in-gmail/29226/