Bravo Jean_Paul !!
I do have these flats at home .... for painting in 2019-21 ...
Your idea to paint the background with aquarelle painting is excellent, as it give a fading tone, which will provide an excellent contrast with the front characters !! (I was more thinking to draw or paint in black and white).
This will inspire me too, but not now, because I am not mastering auarelle paints at all, so many trials to do.
I will be curious to see your work de visu, at some show in 2019?