I am trying to create a news movie, want to have my character in front of a wall with a fixed neutral image and pop an image or a movie on certain parts of the wall (different image sizes / movies to play behind the character as he talks...)

a bit like the video in the following link, maybe more versatile and dynamic with the type of media and sizes that should be embedded on the wall.

http://www.youtube.com/watch?v=VKfA0xN2q-k

I played a bit with the billboards / display boards but they seem to be able to wither stretch / tile the media and I can't find a way to control the sizes.

can you point me to a good tutorial  / any tips on that ?

(i am not looking for a studio look or something like that)