In rails-4, non digested assets are not generated anymore.
If you want to hotlink assets, place a copy of image you'll use in public/
. To avoid duplication, you can use a symlink pointing to the proper location in app/assets/images/
.
It's worth noting that rails does a very good job at caching images in browser, and it is usually recommended to add far future timeout for assets caching in front server. So you should probably avoid to hotlink images that are prone to change often.