Portal!

[Chris2Balls [:B]]

I would heavily suggest you work on sprites at least the quarter of the size of the current ones.

Why?
The bigger the sprite, the less control you have over the pixels, because of all the work it requires. You'll then be able to focus your attention on something far more precise and smaller. Pixel art and spriting are about precision, something which your current sprites lack.

I also recommend you look carefully at Portal references when you do this kind of work, it'll really boost the likeness and credibility of your work.

I hope I've helped.
If you have any other questions, I'd be more than pleased to answer them!