(First of all, english isn't my natural language so maybe this text isn't exactly correct)
You can see the construction process step by step here: http://postimage.org/image/oo36hdtz5/
This was my 3rd digital paint. I never drew before, I just jump to digital paint after I bought my Wacom, so it took me a long time to reach this particular result (about 20hs). I really expect critics, I'm starting at this, and this page have been helpfull. Thanks and I hope it's okay if I leave the link to my devianart page, so you can see a bigger version of this piece, and others personal drawings and 3d work.
http://jota-ka.deviantart.com/
By the way, I used Photoshop CS5 to draw, this was very useful, because I know the tool for years, but I never used for this purpose.
Good bye!