Wizard Photographs

[galaxylei]

No: HPFGUIDX 42335

(I don't think this subject has been covered; if it has, sorry)

We know from the books that the people in magical photographs move.  
What is it about the pictures that allow this to happen?  Do they
capture a bit of the person when they're taken, or a short time span?

Also, once a person is in a picture, does that picture of them take on
sort of a life of it's own--will it change its personality based on
where the photograph is kept or how it's treated?  What happens if the
photograph gets cut up, to make a collage or something?  (Do wizards
just not do that?)  Would it hurt the people in the picture?

-GalaxyLei (first post here btw, hi!)