Just like SMS, when Plivo receives an MMS on your Plivo number, it makes an HTTP request to the message request URL configured for that number. In addition to the regular SMS parameters, the "Type" and "Media" parameters will also be sent. Since there can be up to 10 images in one MMS, the "Media" parameter is structured as "Media0", "Media1" , "Media2" and etc. 

Connect with support@plivo.com to get added to Plivo’s MMS private Beta.