Using women in advertisements of any kind is Haram, even with Hijab. Not even covering the head and that makes it extra Haram. I realize that this trend could be coming from the liberals of the Muslim society, and that they CAN now be taken as examples "because they are Muslims".
Just sit and ask yourself, at the time of the Prophet Muhammad (PBUH), if there was a women's clothing trader (and I assure you there were many), would the Prophet allow a woman to go out with her hair uncovered and "advertise" for the brand? I am sure you would say no.
May Allah guide this Ummah.