What are the objects around the [portrait of François Ravaillac,][1] the assassin of king Henry IV of France? 

Especially the top corners, and the strange animal in the middle.

Why would these be put around the portrait?

[![The portrait of Ravailllac][2]][3]


  [1]: https://en.wikipedia.org/wiki/Henry_IV_of_France#/media/File:Fran%C3%A7ois_Ravaillac.jpg
  [2]: https://i.sstatic.net/q1c3Gl.jpg
  [3]: https://i.sstatic.net/q1c3G.jpg