Large size image you posted doesn't have same size for width and length, keep in mind icons are square format so your image resizes automatically if you used button manager. For your image to fit whole in icon frame, add borders to original image (around 18 pixels from each side on 330~340 pixels large image) and then turn it into icon.
Icon looks very good, character is nicely drawn and colors are in balance, but consider making whole image fit icon size. Approved.