What is the ruling on designing Snapchat filters (frames) and selling them before they are designed and uploaded, and is it permissible to design filters specifically for Christmas?

There is no harm in contracting for filter design and receiving payment in advance. As for designing filters for personal birthdays, if celebrating them is deemed permissible, then designing them is permissible. However, if celebrating them is deemed forbidden, then designing them might be considered an aid to it, and thus would be prohibited.