There are several routes you can take and methods you can apply, but generally assuming your system is UEFI (you can check that in msinfo32):
Disable secure boot (if you leave that on, this won’t work)
Download this program (HackBGRT) available on GitHub
Unzip it, and run it
Type ‘i’ for install when prompted
You’ll be brought into a notepad window. For more information on how to configure this notepad to do a lot of different things with your boot logo, check out the GitHub and/or the notepad file itself
If you just want a simple boot logo every time you boot your PC, just close the notepad
You’ll be brought into an MSPAINT window, where you can paste in any image you want (NOTE: Make sure the image has a black background, as bitmaps don’t support transparency and WILL look odd if you have it with a different background color)
Check the proportions of the image, save and close the notepad window.
You should see a “HackBGRT is installed” message. if so, reboot your computer
And there you have it! Your image should pop up slightly after your OEM’s (or maybe not your OEM’s at all if you’re lucky!)
You can also change it back if you go into the program and select the “Remove completely” choice, but otherwise, that’s it! Have fun!