Plants, real or fake, will simply be knocked over or destroyed, so it is best to avoid them. A Savannah monitor needs a place to hide. This will facilitate taming. A suitable box should be provided. If cardboard boxes are used, make sure the box is strong enough to support the monitor's weight, as it will sit on the box.
Monitors are extremely intelligent.
Further, anything inside the cage, including the doors, should be strong enough to resist pushing, scratching, and tail lashing. Savannahs are indescriminant, and voracious eaters. They will eat anything they think is edible. As they get older, the size of the rodent can be increased. Aquatic food will be eaten, but not often, thus, it is rather pointless to provide fish.