I've been sketching a few different versions of the flowers out and am thinking that I'd refer to keep the design more line based. I think this would work quite well in a pastel colour, with monotype text over the top. I think the contrast between the roughness of the monotype and the smooth, coloured flowers will be quite nice and would also show the theme of innocence through the illustrations but also bring light to the more serious undertone of the book using the rough, textured monotype.
This was just a quick mock-up of who the cover could potentially look, with the pastel/faded design underneath and quite bold text laid over the top. The only problem I can see with this is maybe because the illustration is quite line based, the text could get lost in it? I could try make the flowers more shape based or possibly just fill them in with a colour and add the detail in over the top. I'm not 100% sure yet, I think I still need to play around with the design and layout of it all and also could do with getting the monotype done and out of the way in order to start scanning things in and mocking them up on photoshop. It might be an idea to make a few book jackets and placing my designs on them just to see how everything could work as a whole.