I don't think I quite understand what you're looking for. You can already take an image map and/or displacement map and "lay" it on the terrain with a specified size, repeating options, etc. Use an Image Map shader, load your image, set it to PlanY projection, increase the size to whatever size you want it to be (start with 1000x1000 if all you need to do is see it initially), and then you should see it projected on the planet. You can use a Default Shader, which has inputs for Displacement, Color, Luminosity, etc. and then feed Image Map shaders into those inputs with PlanY projection and appropriate scale. That's probably the easiest way to get both displacement and color (and opacity, if desired).
Once you have all that working you can turn on tiling or blend it with another shader to get additional control and other effects.
- Oshyan