There is a big difference between complimenting someone and flirting, while most of the girls appreciate compliments, flirting might lead on someone indeed and i don't find it appropriate as long as the flirting guy has no serious intentions.
Taking off your picture won't save you from flirts, they will message anyway (i know from experience). It's not the pictures' fault, as long as they are decent, we don't walk on the streets with our faces covered do we? even strangers can see how we look like
So saying that those having pictures up are asking for flirting makes me strongly disagree!