e.g.
data:image/jpeg;base64,/9j/4QAiRXhpZgAATU0AKgAAAAgAAQESAAMAAAABAAEAAAAAAAD/2wBDAAIBAQIBAQICAgICAgICAwUDAwMDAwYEBAMFBwYHBwcGBwcICQsJCAgKCAcHCg0KCgsMDA.....QhCA/9k=

---

If your text/image is too big, you can make it yourself, type this in some txt file, save it anywhere, then change its extension from .txt to .html and open it
<img src='data:image/jpeg;base64,/9j/4AAQSkZJRgABAQ...BQAUAFABQAUAFABQAUAf/Z'>