Istockphoto, no way! Mirco payment agencies are the bottom end of the industry, with the likes of Getty being the top istock, charge from $1 up wards, and I’m not sure how much of that 50p you get. Getty I think now charge you to put images up, unless you are invited by them. (this might not be Getty, I’ve not looked for a while but I think it is)

Of course, this is just my opinion, in a world of conflicting opinions

Alistair