Those are pretty cool, man. You seem to have a good basic of graphical understanding.
I quite like the green one, it has a good composition and is overall very appealing. The only thing that looks really out of place is the Mona Lisa, but I quite like the skull.
My advice to you would be to use the 'less is more' attitude a bit more towards your works, as your images seem really crowded and some have a bit too many elements, whereas a bit more simplicity would probably work a lot better for it. Try to keep pushing your boundaries and try new things, get to know the ins and outs of Photoshop (or whatever program it is that you use) and try to develop.
Keep it up.