i do a whole bunch of computer graphic and illustration stuff, and my preferred technique is paper sketches scanned in and colored/shaded in photoshop. I usually prefer the sketchy look VS hard lines, but if you want that clean consistent line look you can trace your photos/drawings with the pen tool (in illustrator), and then delete the source image. I dont really like illustrator for drawing, but its great for technical illustrations and graphical layouts.
in regards to your work, its pretty good for a first go, but like said, computer stuff is typically tougher to do than the paper/pencil basics, and its way easier to build foundations there and then transfer it to the comp.