If I go to a Command Prompt window and type
mspaint
I can start another instance of the program. That
to me is an encouraging sign.
I can also go to Start : Run and type mspaint
in there as well.
That implies, you could make a .bat file, and
put something like this in it...
mspaint C:\Downloads\sample1.bmp
mspaint C:\Downloads\sample2.bmp
mspaint C:\Downloads\sample3.bmp
then three windows would open.
What I cannot figure out for you, is how
you'd integrate this knowledge, into a
multi-selection. Maybe it would take scripting
or something (to convert multiple arguments,
into individual program invocations).
Do you actually want to use mspaint ? Maybe
there is a third-party program that has a more
complete feature set, and can actually keep
multiple windows open on its own.
Paul