[DustyPorViva]

First off, the angle that you chose to draw these show no perspective and make the images pretty boring to look at. You should try some more dynamic positions for the objects, it'll really bring more like to your pictures. Then you can start working on the actual pixel techniques involved. you medkit looks pillow shaded, which is odd for a flat surface...(A tip for this is to never outline an outline with another color.) your football has no shading, which in turn makes it look flat. The colors are also on the dull side. You really need to drop the saturation in them a bit.

I think the best out of the bunch is the phone. You show a lot more technique in that. Selective outlining, a bit more choice in color, and overall what seems to be more skill. What you need to do is practice with manipulating lines to work to your advantage so you can pull off the shapes the phone has on it. What you need to do to pull that off is a bit of anti-aliasing. I suggest looking it up, but mostly for a general idea, it's the blending of a line with its surrounding colors to remove any look of jaggedness.

Here's a quick edit I did to show you some things to do to improve the phone, since it was the best drawn of the bunch: