Picture frames are articles with the essential character of holding for visual display photo, print, painting or the like. If there are other incorporated characteristics or features they must be secondary to the expected use of the article. A picture frame that can be signed is still a picture frame. A frame that can hold a picture with part of the surface constructed as a French memo board or a coaster with display pocket... not a picture frame. 

Picture frames come in may shapes, sizes and materials and may have a wide range of secondary features. The starting point for finding and determining HTS codes is based on the material used to make the presenting structure of the frame. Commonly this is the "profile" but may take less obvious forms such as glass frames where "frame" and glazing are one and the same or bent acrylics where the object is one continuous article. 

The material of a frame, that which holds the presenting structures together, is the starting point for classifying Picture Frames.