Dynamically replace content

Hi,
Does somebody knows how it could be possible to dynamiclly load content (i.e. text from a external text file or images placing them as posters on billboards etc.)?

I would like to make a real time marketing project where an user enters an environment which is personalized. He would see his name somewhere, then his photo on a wall etc.

Apreciate any tips in advance.

Thnx,
Zoran