i know the 5 digit thing is for specialty services. like those dumb jokes that you can get daily to your phone, or googles SMS service.
sending pictures you can do with MMS. with sms and mms you can send to an email address which would probably be easier to do then with the 5 digit numbers. with TA you set up an email address like email@example.com
and send the pic via MMS.
so setting it up on a server side wouldnt require knowing anything about cell phones if email addresses are used, you just need to figure out how to convert a message with a picture into a thread or something. . .