Send event (printf function) works fine for pdf documents, but it doesn't for image files like jpeg, tiff and other...

 

What function will print images?

I notice that you are a Mac user, so I can't assume this is the same, but on Windows, using Send Event["aevt";"pdoc";"<filepath>"] will print any sort of document if (and here is the key), that file type has the correct definition in the file associations.  If you can right-click the file and there is a "Print" option, then the command will work.  If there is no print option, it won't.

 

You can change the file associations and commands if you try hard enough.  Earlier Windows versions weren't bad, but Windows 7 and 8 hide it from you.  (I recommend http://www.nirsoft.net/utils/file_types_manager.html as a reasonable editor).  For instance, I don't like the Microsoft-supplied picture printer, so I use IrfanView to print.

 

Given how integrated the Mac is, I would be surprised if there wasn't a similar (and probably more user-friendly) method in place.