What effects would testosterone supplements have on mans appearance?

Depends: Testosterone in adult men with normal virilization will notice no change. Very large doses used by body builders will cause increased muscle mass, very small testicles and infertility. So called "supplements" do not cause any change in testosterone or men's appearances (except that their wallets will be thinner).

Optimization: If you are deficient, supplementation to optimal levels (high physiological range, not the "''roid" range used illicitly by some body builders, should result in decrease in "centripetal obesity" (fat around the middle and better muscular development (if you are "lifting" or working out). If you are on too much, you could have undesired effects ("man boobs") because of conversion to estradiol.