Thanks for this, here are 2 more methods you can use for the (almost) same results.
Magic Button :
Method #1:
Every picture on those stock sites have a picture id (all numbers). Simply search Google for the ID# and viola!
Method #2:
I just found out about this method yesterday while looking for some images for site...
...here's the search term for Google Images: "keyword huffingtonpost 1000" (without quotes, obviously)
The '1000' in the search will tell Google to spit out any images with a 1000px width and/or height. The 'huffingtonpost' in the search is fairly obvious - I found that site has very nice high quality photos.