[haunter]

It could be pretty good. Here are some things I've noticed just glancing at the tank:

Parts of your tank change size/shape in the different sprites. Your door seems to shrink when it opens... and on the turret sprite at the bottom left, the door hole is oval, whereas the door itself looks to be round.

Shouldn't the hole for the main cannon be round?

You're definately going to need atleast 8 directions for this tank... Body and turret.

You should slow down. Do one bit at a time... First make sure the basic shape is perfect, perspective is key. Then work on the line details, here you can fill in block colors to make it easier to tell what part is what... Only when you're completely satisfied with the line-art should you start to shade in your work.