I take a better interest of people who at least put up a picture on anything other then no picture at all.
reasons why would be that when they have no picture you get this feeling of " what do they have to hide" feeling or a feeling of mistrust.
this might not be how others feel but I seem to get this feeling. However I prefer that they have an image of themselves, this shows initiative and this also shows that they make an effort in their profile and most likely will show this effort in there writings.
hope this sheds some light on it for you.