I'd work on the sky a bit more, have a lighter blue at the bottom and work on the clouds some more, Diane gives a pretty nice brush for clouds and random texture http://dianae.deviantart.com/art/Why-don-t-you-do-right-73387404
my two other pointers would be, considering the base of the rose and your character are about at the same distance, they should be affected by the same kinda area effect, but they all seem to have their own shade purple or blue when it comes to shading them which sometimes make the whole thing a bit uncunsistant? And finaly, I took of the bird and sun, the birds because they were more of an eye distraction, and the sun because if it were to be there, you'd have to shade your character in consequance, which is "a contre-jour"...what ever that is in english xD
oh and I love this book, and you sure got the rose's attitude right :p nice job

-Let us take over the world with largely exagerated facial expressions!-