You have two options:
- Upload an image file as a binary file to its own tag using a full path
- Convert your image to a base64 string, and upload load that to a tag, or as a part of the tag's value. You will need a base64 extension for this.
(you might want another extension to resize images to reduce file sizes, base64strings tend to be 1.3 x the size of the image file size)
You may need to explain your security/proivacy concern in more detail, this part is not clear.
You may find this useful: