The yuri one's not very good, and I'd recommend not posting much like it on here, since the rules exist and you'd probably get a warning after a bit.
As for the others, they're alright I guess. Vader's head looks a little disproportionate though.
I also have some decent stuff in my scraps, but this is pencil and paper, sharpie, or digital. Those are the only available mediums at home. Back at my school art class though, chalks were a strong point. Lets just say I have bragging rights and a place in the yearbook.