Adding MMS seems trivially easy. Maybe I am wrong thouhg

Seems like just adding a media url is all that is necessary. I tried this and it works.

Promise.all(
  numbers.map(number => {
    return twilio.messages.create({
      to: number,
      from: process.env.TWILIO_MESSAGING_SERVICE_SID,
      mediaUrl: ['https://mediaurl'],        <---- just add a url
      body: body
    });
  })
)