Solved Curious images after shut down

This isn't a problem, but I don't recall seeing these images until 2-3 weeks ago. I'm running the most recent update to my Windows 11 PC (at least per Windows Update), Win Home 22H2 Bld 621.2283. When I shut down my Dell AIO computer I see these two images, one after the other in the lower right corner of the dark screen, and each lasting only several seconds:

(The light circle below the second image contains a question mark) I've never had anything connected to either port, but just wonder why these images appear. Thanks for any ideas!
Gini

My guess is it's connected with the OSD/HDMI-mode button next to the power button.

Perhaps you pressed it by mistake when reaching for the power button?

What does your manual say about the OSD (On Screen Display) button?

Thanks for the reply! I do not use the physical power button to shut down; rather, I use the Shutdown short cut on my desktop:
C:\Windows\System32\shutdown.exe /s /t 0
My manual does reference a "Display Built-in Self Test button/Input-source selection button",
but it is recessed and has to be accessed quite deliberately. To my knowledge, I've never used it, but I'll try to investigate further, perhaps via Dell.

I get different images on my monitors, Dell 24" and ASUS 27", but only after the computers have turned off, attribute it to loss of data signal from the computers, go away soon.

Thanks, Berton! The quickly disappearing images are harmless, and I think I'll let the sleeping dogs lie!