The mix of raster and vector is a bit jarring for me, I think you should just trace the guitar, exaggerate it a bit and keep it all the same style. His black hands blend into the guitar and it's a bit hard to see, you might want to make stand out with a different color or even make them bigger. His expression seems a bit blah, you've got a nice cartoony style, I think his face should match it. He's more of a Johnny Cash imitator to me.