Ensign
Ensign mod offers extended capabilities for working with banners in Minecraft, adding new shapes and display settings.
Banner Display Settings
With Mod Menu installed, you get access to fine-tuning banner appearance. You can disable animations or increase banner sizes. All these parameters work exclusively on the client side and don't affect other players.

New Banner Shapes
The mod adds several original banner shapes that can be used to create unique decorations.
To change the shape of a standard banner, create it in the usual way, place it and click on it with shears. The resulting banners retain all properties of vanilla counterparts - they can be dyed on a loom, and the shape is preserved when the block is broken.
From left to right: standard, swallowtail, tongued swallowtail, rounded
From left to right: Danish, Swedish and Finnish naval flags

Creating Custom Shapes
For creating custom banner shapes, refer to the relevant documentation.