The chandeliers in the same large room should definetely look nice together. And in some cases they be identical.
Each chandelier should be located in the center of the zone that it refers to. For example, if it is a chandelier for a dining area, then it should be placed right above the center of the dining table.
First of all, you need to decide what zone is the major one in your large room. This zone should have a bigger and more significant chandelier than the other one. And all chandeliers that you have in one room, should obviously work together.