I know I am a bit late to this. In featured servers some of the entities or I think they are entities seem to have a new geometry, is their a way in PMMP to make this possible?
Yes. One way to do this is to create the custom geometry.json in a modelling software such as BlockBench. Then when setting a players skin or entities skin you can set it to use your custom geometry file instead of the default. Here are some examples of plugins using custom geometries: (hope this helps) - MyEntities by benda95280 - IsPregnant by thebigsmileXD