I see you just coloured the sketch... well thats one way to do it, but not the perfect one
I guess you use photoshop, use the pen-tool, I know its hard to learn, but it will pay off
That way you will get much better lines.
I like the pict, though there are some odd things in it, like not symmetric, I got the dame problem, it wil get less if you practice more
And tuts on the net are usually good, you learn alot from them.
I dont want to make a negative post, just some comments, keep up the practice
I know I will, just ordered me a Wacom Tablet
:D