I use these and the other 2 packs of face cards in my weekly Dungeons and Dragons games. As I write my sessions or read my pre made sessions I pick out the Face Card most appropriate for every major character and I put them on a magnetized dry erase board, my "Murder Board". I mark the players in pink magnets, the helpful NPCs in green, and the bad guys in red.
I also use the Paizo item cards to keep track of pertinant plot items and unidentified potions and magical items the players have.
As of yet, in this pack and the other 2 sets of face cards (Enemies, and Friends and Foes), there is not alot of diversity, most of the pics are human. A few dwarves, a couple halflings, and only 1 male gnome out of all 3 sets.
As a GM, it makes it easier to keep track of all the plot points, and my players arent as confused about who is doing what, and why they are doing what they are doing. I reccomend putting the cards in penny sleaves as the magnets could scrape off some of the image.