the corners also look kind of dull try adding a border with a size two brush and then decrese the opacity and erase around the parts where it covers your render but dont go out of you color scheme
i like everything but idk if it is just me but i am a bity distracted by the pink in the top right corner. but other than that i love it. and do u have a tut i can do that resembles the style of background you did ?