Interesting work, overall - you've got a wide range of styles you're experimenting with here, and that's good! I feel like your manga-esque work could use a little more attention to line weights and values. A lot of the panels feel very flat. But, I really like your more realistic/painterly work, such as the second to last piece with the girl looking to the upper right. These have a good sense of value and form. One other thing to watch out for is being too casual about finishing up pictures, i.e. getting too messy with much of the piece once you have finished rendering the main point of interest. I see this with the piece with the balcony on the pond, and with the black and white girl with the very sketchy and blocky hair, but very detailed features. This is not to say the peripheral things can't be more sketchy than the main focal point - the difference in rendering just should not be quite so drastic, imo.
I'd love to see more realistic work from you. Keep up the good work!