We have got our ETags and expiry headers setup correctly so when browsing round the site without posting it really is very snappy. However, after any Publish (that is almost almost always adopted having a 302) you can observe the browser re-request all of the images. Can there be something that may be leading to this? It is possible to setting that handles this?

In my opinion typically you'll still obtain a request however with 'If-Modified-Since' within the header -- a minimum of that is what I have observed, despite expires headers. The response ought to be 304 (not modified) that is ultraquick. Or are you currently saying all of the images are reloaded entirely?

Read more on If-Modified Since Read about If-Modified-Since in HTTP RFC