We're interested in making a banner that would be appropriate to the 16th century. So, I started researching to see what shapes and sizes I could find. Square flags seem pretty common for heraldic displays, but there are many other shapes as well. I have a growing collection of pins, but will highlight the different types here.
I pulled this image from a video on "The State Funeral and Heraldry of Mary Queen of Scots", but haven't been able to find more details about the image. I suspect it lives somewhere in the Westminster Abbey Library. It is an inventory sketch of the flags and banners from the funeral and shows square flags and a pennant.
Basic Banner and Flag Types:
Pole on Top with Dags
These are seen most commonly in a religious context, and similar shapes are still seen in churches to this day.
Square Flags
These are often heraldic in design and may have been stiffened as they are often depicted looking quite rigid. Some examples are see in the image above for Mary Queen of Scotts.
Rectangular Flags
These generally don't look as stiff or rigid and the square flags. While they often have heraldic symbols on them, they are not as structured in design as the square flags.
Pennants
Long tapering triangles that ripple nicely in a breeze can be seen in a few different forms. Some are quite narrow and very long (see the ship in the Ommegang painting of 1615; image 17 of 89). Some taper to a single point while others split into multiple tails. They can be quite large as seen in another of the Ommegang painting where there is one taller than a horse and twice as long!