Or you could just "virtual host" by initial URL path, like "hxxp://10.0.0.1/host.sample.com/picture.jpg" or "hxxp://10.0.0.1/p2ezQ/picture.jpg".
Out of curiosity: do you do (or know someone who does) this?
Do you think the functionality is worth the code to implement it?
No idea if it's worth it. Measure. Build a test case that implements a limited version or emulates this somehow. Test it against some group for a few weeks or months. Did it benefit you, made no difference or harm your goals? Did it give you something unexpected that you can turn into your benefit?