As a Roblox developer, the HumanoidDescription icon looks look this (100% and 300% shown):
It looks like a humanoid on top of a script. This is strange.
There are currently 6 other icons that use some variant of the Script icon. The Instances that use these icons are: Script, LocalScript, HopperBin, ServerScriptService, ModuleScript, and the PlayerScripts Instances. These are all meant to either contain Lua code or to contain scripts. HumanoidDescriptions are not meant to do either of these things.
The current icon is potentially confusing and misleading, and should be changed to an icon that better fits the purpose of HumanoidDescription. Personally, I think something like a mask would be great, since the point of the Instance is to change how a Humanoid looks, and it fits with the icons of Shirts and Pants and whatnot. I drew one to see if it was possible in a 16x16 space and it looks pretty decent:
But anything would be fine since the current icon is misleading. If Roblox were to change the icon for HumanoidDescription, it would make the icon less strange in relation to the other ones.