These are Below the Ocean?
You can do Awesome Caverns if you disable BiomeHeight for that Biome. Maybe you want to tinker with that a bit.
That would give your Caves a more Natural feel. (Is a Pain to Adjust for the Borders though)
The Flat Ground and Ceiling gives your Cavern a bit of a Boring/DugOut feeling.
You could add Objects that cut away on the Ceiling and Floor, to give it a more Varied look.
Also, you could consider Planting Jack o Lanterns down there as an additional Light Source.
As for the Ships, how do they get down their? Feels a Bit Weird in my Opinion.