The software "Shell Picture" (http://baxbex.de/shellpicture.html - no freeware!) is very similar to "Shell Extension", but has interesting print functions.
Maybe you can add print functions too?
Peter
SE: Additional print function for Shell Extension
Moderators: XnTriq, helmut, xnview
SE: Additional print function for Shell Extension
XnViewMP 1.6.5 German, XnConvert 1.99, Win 10