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.
If you are designing permissible designs for these brands, then there is no sin that falls on you in dealing with them, even if they are selling some products that are prohibited in terms of designs or others. What is important is that what you design for these brands should be of the permissible designs.
Allah knows best.