Those last photo studies look pretty sweet, when going into memory, try building a loooot of construction lines first.
I always end up with this whole mess of scribbles with construction lines, I've found myself lost sometimes because of my own mess, maybe you should try doing some quick studies with basic construction lines, it helps a lot to master them
Also, I'm a huuuuuge fan of Joker and Harley Quinn, best couple of villains ever, I'm eager to see you do a finished illustration of Harley!
Cheers, mate, and keep up the good work! Don't let those bad vibes from get to you, it's admirable that you work so much and still find the time to work on your artwork, so don't give up!