I think pics of parents are very important. I've seen many amazing looking pups turn out just like thier parents. Sure they are 10 fold as nice as the parents when young, but a majority that I've seen tend to STAY nice IF the parents are nice.
If you're in it to just keep them till they get big then sell them then no biggie, look for the nice ones. BUT, IF you're in for the long haul and will be keeping it till the end, I'd feel MUCH more confident buying a pup with nice parents then a nice pup with average parents.
I could be wrong but till someone shows me the proof I'm sticking with what I have seen.