Nice! You should actually start making your mod now. Lots of good tutorials out there.
Well if I wanted it to look good it would have to have good rendering logic. For now I have just made it a hanging entity , which can be placed on walls. Also since its an entity I can move the player camera to the entity's position so I can spectate it. I have a monitor item which can be right-clicked to spectate a camera. The difficulty is, the monitor has to be able to monitor all the cameras, which means it has to have an expandable GUI with an option to spectate any one of the security cameras you add to the world. In addition that would mean I have to have a GUI for each camera so one can put an id in them, and that id will show up on the monitor. (Its really complicated i know)