Can you use a 1400mAh battery in a camera for 760mAh?

The rating mAh is a measure of the amount of energy that can be stored in a battery. The higher the number, the more energy can be stored. Assuming that the batteries are the same physical size and have the same nominal voltage, there is no reason why a 1400mAh battery shouldn't be used in place of a 760mAh. The only difference is that the larger battery will last longer between charges than the smaller one.