That's to vague of a question, to start.

If the arms are both the same size, then the arm on the left is too low down/at the wrong angle.

It's also lacking cast shadows, and the highlights are quite soft - not really a bad thing, just something to think about.
There are some scattered red and blue pixels, That I assume are lights. These do not read as lights, they read as compression/artifacts. you should use at least a 2x2 pixel size for an isolated section such as a light - it's also somewhat of a waste of 2 colors.

Other than that, You need to ask yourself some questions first:

- What is the purpose of creating this sprite? I assume it is for a game.

- What is the purpose of the Mech in-game?

- What is the back story?

- what are YOU happy/unhappy about, specifically.

Edited by skaytr - 20 June 2013 at 11:38am