The "Charges Will Apply" prompt is to inform you that the phone will be sending a MMS instead of a SMS. Since you say that you have unlimited, (VZW has multiple tiers of "Unlimited" messaging, ex: Unlimited to VZW, and 500 to non VZW; or 1000 to non-VZW, etc., you may or may not get charged, sorry.
However, so long as you're sending the picture to another Verizon user, you shouldn't be charged additional fees, if it's to a non-VZW user, then the MMS will count towards the allotment that VZW gives you to message non-VZW users.
To anyone else, please feel free to correct me, I fear sometimes I might have misunderstood what VZW likes to define as unlimited in their contracts.
