I still don\'t quite get it, where to put images in rails 3.1, in these situation:
Stylesheet images should be placed in app/assets, while files uploaded by paperclip in public/system. In case of assets , fingerprints will be created for every file, so they can be properly cached. If cached file changes, fingerprint changes too and in such way cache is invalidated.
UPDATE: To reference files in app/assets (e.g. specifying image url in css) you`ll need to use special asset pipeline ERB or SCSS helpers (like image-path and image-url for SCSS and asset_path for ERB).