This blog post explains how you can open Windows files from the command line by specifying only the name of the file. You can open the file by name from a Windows command shell or PowerShell or you can invoke cmd.exe to open the file from a Windows Subsystem for Linux (WSL) shell.
In a command shell, you can simply specify the name of the file. Windows opens the application associated with the extension using something similar to the start command.
c:\temp\imagefile.png cd temp imagefile.png start imagefile.png
PowerShell seems to require that you specify the path, likely because it does not recognize the filename extension as a command.
cd \temp imagefile.png ./imagefile.png
WSL seems to make all files on Windows file systems executable, but does not know how to “execute” images. You can pass the file to cmd.exe /c, in which case you likely want to append the command with an ampersand (&) so that you can continue using the shell while the launched application runs.
ls -ltra imagefile.png file imagefile.png cmd.exe /c imagefile.png & ./imagefile.png
Note: possibly coincidentally, brush.exe, which I had been using for storing screen captures, crashed shortly after this last command.