Can you generate procedural terrain based off a custom map's ocean locations?

[Dune]

Here's another setup. Displacement by color can be controlled by the smooth step, either a constant color/scalar or a PF, where color gives the max displacement, flattening near top. You can also play with the color offset in the preceding PF, less white=less peaks. I used a simple shape for the landform, but that can be replaced by an image map.
The second surface shader offset displaces the whole seafloor down, the displacement tab up again from the PF. If you raise that above the downward offset, islands will appear. You can see where it's just below sea level, foam appears (from the displ to scalar line).

[AlianaAR]

Here's another setup. Displacement by color can be controlled by the smooth step, either a constant color/scalar or a PF, where color gives the max displacement, flattening near top. You can also play with the color offset in the preceding PF, less white=less peaks. I used a simple shape for the landform, but that can be replaced by an image map.
The second surface shader offset displaces the whole seafloor down, the displacement tab up again from the PF. If you raise that above the downward offset, islands will appear. You can see where it's just below sea level, foam appears (from the displ to scalar line).

Interesting rig for me to study. I don't pretend to understand it but where would I plug in my land shape map? That has to come from an image obviously.

[AlianaAR]

I have figured it out!

I used Heightfields with the default fractal terrain. Instead of displacing the default terrain I used that displacement map as a Heightfield. This allows separate control over my continent/island fractal terrain from the global default. It holds up at any altitude.

Now that I have my oceans and land figured out, onto global clouds!

[Dune]

Good. Yes, just attach the fractal warp of the default terrain PF to the input of the simple shape and disable/delete the simple shape. You can control the roughness of the landforms by changing the color roughness of the terrain PF, and the amount of ocean by lowering the color offset. Further control in the two color adjust shaders.