Hi! I was wondering if there are any canon descriptions for the appearance of Snape's asscociates at Hogwarts? Namely Wilkes, Rosier, Avery and Mulciber.

I can't find any myself and was wondering if I have free reign with this?

Also if anyone has any suggestions for what they might look like feel free to chip in.

Thanks in advance.

Edit: Also out of these four and Snape who do you think is the most likely to have been made Slytherin Prefect?