As you may know, entity models were hinted for 1.9, then (most likely) scrapped. So, I have taken it upon myself to create a working customizable entity model system as a mod. The ENIM entity model system aims to provide customizable entity models that can be animated with custom animations under a variety of circumstances (as permitted by the game). Entities, tile entities, and items can be modelled under the ENIM model system.
Documentation for various features can be found on the wiki.