All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The use of the photos provided by such websites depends on whether or not they give the permission to do so; one can judge this issue based on the prevailing custom in this regard.
However, it should be noted here that if the clothes that you want to display are women's underwear, then it is not permissible to display them on the body of a woman or a mannequin.
Allah knows best.