Pictures are asked for with some secondaries (most of them, actually, but sometime's it's optional).
I sent all of my LORS as soon as I submitted AMCAS--my premed committee took care of it for me. Howver, some schools request that they only be sent with the secondaries. Then again, it may be better to get them there to avoid delays later on..so I say send them all now, but check the websites of each school you're applying to to make sure they won't throw them away. <img border="0" title="" alt="[Eek!]" src="eek.gif" /> I never had any problems sending my LOR's in early. 🙂