For "a place where things are stored":
* Dispersal: The opposite of gathering things in one place.
* Scattering: Similar to dispersal, implying a random distribution.
* Waste: If something is in a repository, it's usually valuable or important; the opposite would be something discarded.
For "a source of information":
* Ignorance: The absence of knowledge or information.
* Obscurity: Something hidden or unknown.
* Misinformation: Incorrect or misleading information.
For "a place where something is preserved":
* Destruction: The complete opposite of preservation.
* Disintegration: The process of breaking down or decaying.
* Obliteration: The act of erasing or destroying completely.
For "a person or organization that keeps or manages something":
* Distributor: Someone who spreads or disseminates something instead of keeping it.
* Consumer: Someone who uses or consumes something instead of storing or managing it.
* Discarder: Someone who throws away or gets rid of something.
Ultimately, the best antonym will depend on the specific context in which you're using the word "repository."