Hey Clay, thanks for your reply! Messages 2 and 3 do NOT include an Image field in the webhook payload at all. Somehow the personalized image is still attaching to messages 2 and 3. Do you have any idea what else could cause this? I'm using your snapshot as is and didn't change anything except for the phone numbers.

@Frankie Patetta @Clay Lawrence quick question about the master sending account setup with Nifty Images. How exactly do you get the personalized image to send as MMS through the master account? Specifically: 1. What do you put in the sub-account webhook custom data fields for the image? 2. What goes in the master account SMS step for the image/attachment field? 3. Do you use a contact custom field, a custom value, or something else to pass the image URL across? Been stuck on this for a while — the image sends as blank or invalid URL. Thanks!