There can be a number of reasons why there is no picture.
Some TN members are in the sort of work where they cannot risk being identified as nudists. Others are just shy. This is made sharper when we realise it is often easy to access members' photos by just Googling the user name and clicking on Images. They can be totally sincere nudists.
In completely the opposite vain I get suspicious if they are not cirtified AND there is no profile information. I get very suspicious if there are no friends or groups as well. I have been scammed by someone pretending to be a young, single, female nudist who wanted to deposit a small fortune into my bank. I'm not that gullagle. You probably know the scam. When I looked up the country of origin there turned out to be a whole bavy of them, all from the same (non existant) refugee camp. The presence of a profile photo is no guarantee, however, as they can "borrow" one