Yes, you can certainly add your own tracking pixels to content created in Delivra!
Navigate to the HTML section of the Drag and Drop Editor. If you have HTML editing permissions, you should be able to access the code of the email content.
The pixel should be an <img> tag placed at the very top or very bottom of the HTML tab of a content file.
We do not recommend editing the HTML of a Drag & Drop Editor based content. Should you need assistance with a content file that has edited HTML, investigation and/or a resolution could result in billable time.