Back charges for both text and photos

[surfgatinho]

I've heard that you may charge retrospective royalties on images used without permission on other websites. Having around 5,000 unwatermarked photos up around the web I'm sure more than a few of these will have been lifted (including one I found on one of the UK's biggest seafood companies site!)

So, can I claim back-dated royalties. And if so is something like Wayback Machine (The internet archive) sufficient evidence? Also what rates can I charge - can I use Getty or Alamy as a benchmark?!

The other thing I was wondering is does the same apply for text. And if so how much is a reasonable charge?