how do i send a picture or multimedia message to a cricket phone via e-mail?

Simply send it to the Cricket subscriber's picture messaging e-mail address.

Cricket subscribers can receive messages at yourphonenumber@mms.myCricket.com. For example, a customer with the phone number 123-456-7890 can receive a message at 1234567890@mms.myCricket.com. 

If the recipient's phone cannot receive picture messages, they will receive a text message with a link to a website where they can view their message.