What are these little things on the evacuation slide?
@ratchet freak is correct. The protrusions are canopy poles, where the canopy in the evacuation slide/raft is propped up. The image below shows a canopy propped on them.



Image from tulmar.com

From the document:


  The canopy is supported in the center in 4 places by inflatable yellow “CANOPY END SUPPORTS” and “CANOPY CENTER SUPPORTS”, and supported along the sides by 14 numbered supports on the top of the slides inflatable structure.


Here's a closeup of the support from the same document.