Proxying User Images

I have imho, a slightly simpler solution to this for only $20/month.

Still using Heroku, I just use a simple nginx buildpack configured to provide the reverse proxy to my origin server. Unless you have massive traffic, you probably only need their free tier dyno.

I then setup DNS to have cloudflare in front my Heroku dyno so everything is nicely behind a CDN and SSL. With the rest of that $20/mo, you can also put your entire domain under SSL.