FHIR Patient Resource has a photo variable:
photo 0..* Attachment Image of the patient
Questions: Are there examples for each: How do upload a patient photo (what format are supported etc). How to retrieve a patient photo?
This post How to Get FHIR Photo for Patient from a URL seems to be old.
Patient.photo is an Attachment which contains Attachment.data, which is a base64Binary. So you just base64 encode the image and set the proper contentType.
I uploaded you a patient with photo here: http://fhirtest.uhn.ca/baseDstu3/Patient/70691