And that's it!
With more time I can paint and sew real sleeves to the shirt, make better horns in helmet and on back, tailor it to better fit him, but... I'm really happy with the final result, I only work for five or six hours on this costume and including all materials I spend no more than 12 €uros (something like 15 or 18$)... And compared, a costume "made in china" cost something like 15 o 30€uros and is of worse quality...
And remember, I post this guide more as a reference than as a "must follow this steps to do it well" ;)
P.S. I need to give a big hug, a patch, greetings, regards and lots of thanks to instructables's member jessyratfink who kindly helped me to fix my bad (or maybe not so bad? :P ) english for that instructables!