It’s lazy summer time and I’m not super productive at the moment. However, I love to have a uniform style of my MacOS app icons and noticed that the ones from Engine DJ and SoundSwitch (but also some other ones like Office, VLC and Audacity) didn’t fit to the rest, so I changed them with other variants from the web.
As for SoundSwitch and EngineDJ, I designed two custom ones. Feel free to download the PNGs to replace the stock icons. Disclaimer: These are not officially ‘approved’ and just a result of some boredom shenanigans from my side, so I hope the mods don’t mind.
The procedure is very simple: Select the according app in the finder, press CMD+I, and in the information window, drag the PNG of your desire onto the small icon in the top left corner, then close it and restart the application. You might have to remove the app from the dock (if pinned) and add it back in order to make it refresh - voilà. Have a nice vacation time 
