I was able to make it work ... partially. The image now appears as an attachment.

function sendEmails() {
  var templateData = getData("Templates");
  var emailSubjectTemplate = templateData[1][0]; //Cell A2
  var emailBodyTemplate = templateData[4][0]; //Cell A5
  var emailData = getData("Data");
  var logo = DriveApp.getFileById("1PyDU0sOYW_OSMQ1vNpXn9JGf7-I7_dBL").getAs("image/png");
  emailData = rowsToObjects(emailData);
  emailData.forEach(function (rowObject) {
    var subject = renderTemplate(emailSubjectTemplate, rowObject);
    var body = renderTemplate(emailBodyTemplate, rowObject);
    let emailImages = {"logo":logo}
    MailApp.sendEmail(rowObject["Email Address"], subject, body, {inlineImages: emailImages});
  });
}