Protonmail Unknown embedded image (.png file)

I responded to a nearby CL add for a vehicle using my Protonmail account that is only used for online deals. The seller responded and sounds (reads) completely legit. When I responded back I noticed there was an embedded .png file that I did not embed.

I ran the file through several AV's and nothing came up as an AV, ransomware or anything else. I also ran several full scans and there are no threats shown.

Disconnected from my network I clicked on the .png to see where it led. The .png file opens an image of my desktop, shows files and folders (that are on the desktop). But it is more like a screenshot because none of the files are viewable or executable and when a folder is open, which I know contain files and photo's, it shows nothing.

I do recall seeing embedded files in other emails I sent out from my primary Protonmail account to people I knew were legit. But this is the first time I have seen an embedded image in an email, that I sent (replied to after the initial exchange).

If this is not a virus, malware, ransomware or something else of that nature. Any idea what it could be?

I have searched for this issue and dont see any other posts and I have emailed Protonmail but have not yet received a response.