Someone had posted this
Pricing and I haven't really had time to read it all but you might find some guidance there.
Last year I sold several shots to the Government Travel agency and they paid $500 per image that gave them 5 years to do anything they wanted except selling them. I still retain the copyrights. But a truely unique shot could be worth 5-10 x that.
I would say a bare minimum is $250.00 and up per image. It's very different than selling a print for $50-60 per because they will use them in many ways.
You need a contract so that you get credit on them and have clear terms about selling etc.
There was a thread about this that I'll try to find.