I found this amazing picture on Pinterest before - I would love to create something like this, using layers and layers of fabric. I know how tactile and varigated even boring cotton fabric can be when you look at the edges, this effect could be created with so many different kinds of fabric.
I'm guessing the best way to start would be to create a 'topography' kind of map for the design, then cut the fabric into panels to fit the shapes, and see what emerges!
I did a sketch a long time ago of a rockpool in a similar vein, you could embroider onto the different layers to create more interest, things like shells or seaweed.
Mmmm, i think i need to think about this one.