A link to my warcraftpets.com collection is here.
As of Friday April 3, 2015, my account has a nice collection of battle pets. Not nearly as many as the serious battlers, but good enough for most of the pet tamers.
Warcraft Pets list the top 20 battle pets, voted by the forum members.
I have 1, 2, 4, 6, 7, 8 , 10, 12, 13, 14, 16, 17, 18, 19.
As I don't do dungeons or raids any more, some are not available to me. I also do not buy from the Blizzard pet store.