You are the third person to use the same stock. First one is looking good, a small text would've done it a complete one. Second: Looks good, you'd added a blue/green light. Third one looking a bit good too. Fourth one doesn't fit what you wanted to show in that avatar. Fifth not much effective looking similar to 3rd one. Though a good set of avatars. You should try giving lights in different modes and always play with opacity. As well as lights you should try adjustments such as Vibrance, Expulsure, B/W as well others in different opacity. Try playing with opacity and stop when you are satisfied try mixing lights and many things. BTW Good work and you will improve to a great extent in the future.