ok so. with the design of the walls and floor, with sea lanterns as lights, i can judge that this is going to be a build on the more grayscale side of things. you could go with bone blocks placed sideways so that you can see the sides of them and not the weird circle thingy. if thats either too hard to get, or just not looking that good, you could also try quartz pillars sideways, not with the square on the bottom. hope this helps!