I've been on a deep dive with Houdini over the last month after switching from Blender for my game development pipeline. I can't overstate how much I already love this tool, what a revelation, so thanks to everyone at SideFX.
One thing that's been bothering me though is the dated look of the current stock icons bundled with the application, especially in the context of MacOS Big Sur. The only reasonable course of action I could see in response to this was just rolling up my sleeves and making my own version of the icon in Houdini itself as a learning exercise.

I've attached the final result, and uploaded the icon files here [gumroad.com] for free if anyone wants to download and use them on their own machine. I'm rendering out the light variant as I write this so that'll be available soon if that's your preference.
That's all for now, thanks!