Thank you for your suggestions, most of those I hadn't actually noticed or considered until now. Always refreshing to get new perspective from experienced artists =)

Here's a few suggestions:

• The white background isn't necessary, and makes things look cramped because the tank is pressing against the edges. Make it transparent instead.

• The entire tank is side view, so we shouldn't be able to see into the muzzle of the cannon as if we were looking at it from an angle. Just make a straight vertical line at the end.

• I like that you chose a light source and stuck with it. I think it would look more natural if wasn't concentrated on two points. Try extending some of the midtones of light across the top of the turret and the top of the tank body. There's already a thin line of light grey in those areas but I don't think it's enough. Also add a little bit of light to the barrel of the cannon.

Your circles and other curves look good. The thick lines you chose aren't often used in pixel art from what I've seen but I like the way the heaviness of the lines seem to make the tank look and feel heavier. If you want any other suggestions or to let other people make constructive edits to your work so they can better show you what they mean check out the WIP section of the forums here.