Wormwood said:
The Player's book is about the players---they should be the focus.
I'm going to have to disagree with you (and apparently WotC) there.
They have the character sheets, which is for PCs only, so they can use the Posing PCs image (either of the two) for that cover.
However, the PHB is arguably the most important book for the game. I think it should focus on the adventures as opposed to just the PCs or the dragons.
I will agree that the dragon takes up a lot of the cover space, but the piece isn't about the dragon, it's about the fight with the dragon. But then again 'dragon' takes up a large portion of the game's title as well.
Comparing the two images the dragon fight gives me more of a sense of 'possibilities' than the other two covers do:
It's got humans, an elf and a dwarf.
It's got a fighter, probably a rogue and a magic user of some sort.
It's got swords, a magic staff and a couple of maces.
It's got scale armor, leather armor and robes.
Oh... yeah... and there are rumors of a dragon in there as well.
That says 'adventure and excitement' to me a lot more than 'a flesh showing girl and weird critter' do.