Arturo, first off, welcome aboard.
Now, if this is only your second bust I'd say you have a pretty good grasp and you are well on your way. I'm assuming you're using acrylics, so I couldn't be of much assitance other than to say a bit more definition in the facial work and cap, shadows and highlights. Review and study works from other fellow "paint sniffers" and see how they create definition and depth. Practice is the key, and have fun.
Great work, Arturo. Cheers, Ski.