You should be able to access the picture messages sent to your child's phone from www.vzwpix.com, although I'm not 100% on that. I'm not sure if you can see sent pictures here...contact Verizon Customer Service if you really need to know.
I would like to agree with PrettyPlease and say that you should trust your child to be mature enough to have a picture phone without having to snoop into what they've sent/recieved...if you don't believe that they are, they should not have a phone, period.
Yes, you are able to view all the sent and received photos on Verizon. The pictures can only be view on the phone it was sent to or from, or also retrieved from Verizon with a court order. You can get more information here http://support.vzw.com/faqs/Equipment/hub.html.
Perverts after unsuspecting children, it's not just a manner of trusting your child. My best friend just found out her daughters Kav Maga instructor had sent her naked pictures of his self, she was 17 he was 48. Had no idea this was happening, daughter was impressed thinking this meant she was special not that he was a pervert, you have a right to check on and protect your children.