I had some tentative discussions with Solent News a while back, but they went no further.
With all of these deals, the key thinks to think about are:-
What's in the contract? Is there a sub-licensing clause?* What triggers payment? What percentage?
What is the average license fee they charge? How likely will my work attract top fees?
If I were to contact the picture desks directly, could I make more money with less effort?
Anecdotally, I have heard that licensing fees for use on some very high profile websites can result in a mere £10 into the creator's pocket. And this is for a site receiving hundreds of thousands of hits a day. And the terms usually mean the use rights are in perpetuity - in other words, forever.
And these popular sites are then scraped for content by the infringing masses...who then use your work for whatever purpose they see fit and yes I have seen my own work ending up in some very unsavoury places that would not have been licensed under any terms.
So you need to do a bit of homework. Figure out what the likely return is** and make a judgement call. If you can't guess already I'm not a fan and my work does not end up with syndication agencies.
*I can go into more detail about why sub-licensing clauses are the work of the devil himself and are to be avoided at all costs. Been there, not good.
**If they won't tell you, or give you a rough idea, then this would ring alarm bells.