Hm. Your (metrotor's) style is pretty good, but drawing stuff (ex. characters, backgrounds, items, etc.) from yourself would be more original, even though you've been doing good job with all these sketches/artworks of yours.
So, you just sketch them without having a picture under it (the paper), right?
Usually if you do that it might look more worse than the original picture/character, if you're not a super master drawer, who can keep his/her hand very moving/flexable.
Have you considered of using ex. This one line/box technique, where you'll draw ex. 17x20 boxes around the original picture, usually printed or so, and then you start drawing the picture you chose to another paper ?/.
A little waste of paper, though.
Anyway, your artwork seems good, but using some shadings might be slightly better in some of them or so.
And usually when colouring things, you'll have to think about the shadows and the lighter shadings ex. Where is the sun coming and how is it affecting the character's shadows and so.
Colouring isn't that hard, only thinking about the lighter shades and the shadows might be hard, of course choosing the right colour(s) (panels) might be slightly medium-hard or so.
Oh, and sometimes shading-in-shape is also very important; Don't make just straight lines on some character's (ex.) body or face.
But when thinking about mangas in general, some of them do have very heavy shadows and so, if they're only black-and-white (ONLY black and white colours, no grey).
Good job, keep going.
Maybe try drawing some Pokemon next time, huh?
Bulbapedia might help you with that, it's a "wikipedia" for Pokemons and other Pokemon related things.
Also, maybe some Mario character would be fine, too or Sonic character, if they're not too hard for you. And try doing backgrounds, too, even if they'd have to be very simple and so.
Not need to, but just saying. It would make them look nicer and so.
Of course the background needs shadings, too. That's why it might be harder to make.
As an artist and a photographer (I do both sometimes, but I don't use my pictures in my drawings usually) I have atleast a little bank of knownledge about shadings and so, but sometimes I favour line-art more than fully coloured or black-and-white art.
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Deni123, did you ask a permission for that graffiti? Just asking.
Nice job, too, not much to say about it. For a banner it seems like a good one, that other job you did. The shadings are nice in the ball, the text is nice and so. I wish that was/is the original picture, though, since that one might've gotten removed.
Your friend's graffiti looks cool. Urban styled, a bit funny looking.
Truely, nice text-art. As a just-line art, it looks very, well, curvy and so, to say. If that would be a Font, I would use it sometimes to make interesting things or nicknames with it, haha.
Good piece, but not that hyper special, as it's just text and so.
Otherwise, nice, mildly needing of colouring/shadows, maybe, but is good the way it is.