I never said he could not be human looking, just that he has to look different in some way to reflect the fact that he is not the same as the people he is around. Even if you don't want to go full dragon imagery, he at a minimum has to look different from his family to me.
Hawaiian or some other island nation ethnicity is my go-to as it can reflect people not knowing much about dragons. As it is Spike doesn't look as adopted as he should be to explore him not feeling as if he belongs.