In the Ruby on Rails guide to the Asset Pipeline, it says
Any assets under public will be served as static files by the
application or web server. You should use app/assets for files that
must undergo some pre-processing before they are served.
http://guides.rubyonrails.org/asset_pipeline.html
To me, this says that images should be kept in the public directory as they can be served statically by my web server and require no pre-processing.
Are there advantages to putting your images in assets/?
Asset precompile appends unique hash value to image filenames, which allows users to get latest version of it despite of cache or expire settings on the server. This is useful when you want to change images in website design.
You don’t want to use
/assets/imagesfor images what are unlikely to change (like user uploads).