I actually do like how you did Hero and Shadow...Mali, on the other hand, needs to look a little more African-y; I don't know how to put it, but his hair (while it is the right color) is not quite the right texture...it's more along the lines of um...well, it kinda resembles Goku, and his nose does kinda need to be redone. I'd recommend looking up some black male faces and basing his appearance off of those (their skin is literally black, but their features are also based on black people. And their wardrobe is more tribal)...sorry if I sound harsh, they're not bad drawings at all
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)