guys, you took me wrong. I don't care about whether an image is in cache. Rough example:
assume the cache is clear, now application started and downloads images 1 and 2 from a storage, if the page is refreshed those 1 and 2 images will be fetched from cache. Now new version of game is coming and the 2 image is updated and 3 image is added. The 3 image is not in cache so it's downloaded automatically from storage but the 2 image is IN cache and will be fetched from there by normal loading unless a timestamp is used for example. So I need to make sure the updated images will NOT be taken from cache.
How to figure it out? Using a proper timestamp? By images renaming? Sending to client the list of updated images?