Wa aleikum Alsalam, I hope Your Clothing line be successful!
Firstly, Clothing is absolutely (Halal) but there are exceptions (Haram) such as inappropriate clothes (skinny that may show the parts of the body that is prohibited to show it, does not cover those parts of the body, etc.)
Secondly, ِAbout the photoshoots in general, there are difference in scholars sayings, to be honest there is a big scholar that prohibited photos.
As prophet muhammed (peace be upon him) said:
"The lawful is clear and the unlawful is clear, and between that are matters that are doubtful (not clear); many of the people do not know whether it is lawful or unlawful. So whoever leaves it to protect his religion and his honor, then he will be safe, and whoever falls into something from them, then he soon will have fallen into the unlawful. Just like if someone grazes (his animals) around a sanctuary, he would soon wind up in it. Indeed for every king is a sanctuary (pasture), and indeed Allah's sanctuary is what He made unlawful."
so I advice you to leave photo-shooting because this clothing line will be a way to earn money, and if photo-shooting was haram it will be a problem, and try to picture the clothing itself without the needing of a human (person) to wear it.
Thirdly, In addition of what I said (Secondly), also photo-shooting a mature women(girls) with hijab on head is not a good choice since women(girls) will try to show the beauty of the clothing, and without hijab either in clothing pictures or not it is also not a good choice since you are not 100% sure that all the people who will look to the picture in the website, application, shopping mall, etc. are women(girls), it is Haram, avoid it better.
Fourthly (adding from me), be sure whenever you do something or avoid something for the seek of Allah it will be better than if you did not, make your best and work on the clothing line plus do not disobey Allah or forget him.
Resources(most are arabic try to translate some if you want to be sure)