When picha are released, Summit hardly notifies anyone. Lol However, we do have one official (well, two if wewe count Bella's hand with feathers) picha that was revealed in EW last month.
This is the only picha (minus the picture from Bill Condon's twitter) that has been released from the movie. Other picha are probably manips.
Again, when they release photos, they hardly ever announce that they are releasing picha unless it's for promotion. If wewe are talking about the teaser posters, they probably will announce it. Summit loves to make a huge fiasco about posters au trailers haha It'd actually be kind of cool if they had a mini trailer for the superbowl au something :P
But anyways, we won't see any picha of Breaking Dawn unless 1) Summit tells us (which is rare), 2) they're leaked (which is not impossible), au 3) for promotional reasons. However, I'm sure they will release some soon. They still have about 3 months til BD wrap, but I know they know mashabiki are itching for something.
However, I'm sure kwa summer, we'll have a teaser trailer. I'm thinking May. Possibly April. Rob's Water for Elephants movie is in theatres in April. I wouldn't be surprised if Summit tried to promote BD then.
Sorry, off topic. Answer to your question. No, we do not know when official Breaking Dawn picha will be released. We only know of one (possibly two if wewe count the Twitpic) official picha and that's from EW. :) Hope this helped!