I would like to suggest:
1) in backend set up defaut cover (if user didn't chise one during registration).
2) keep on site 2 default avatars and 2 default covers based on Genre.
So if user didnt uploaded avatar, we still can know is he a male or femail just looking on his/her avatar.
Also pre uploaded covers would be good (like avatars).
Thanks.
P.S: JomSocial allready use it for example.