Great Concept!! I didn't think about this Challenge's theme in a positive way, but it can definitely be a great thing, some peace and quite :)

I would suggest you to play around with the colour balance tool after you are done colouring. It helps to get all the colours in the right hue (without having elements popping out too much and looking like they don't belong in the same piece), and makes it look more clean :) . Other than that, keep up the good work :)