Adding a logo in a pdf by Ghostscript

Question

I am trying to add a logo in a pdf by Ghostscript. Currently, I am adding a text with the use of this Postscript .ps file:

<<
   /EndPage
   {
     2 eq { pop false }
     {
         gsave      
         /NimbusSanL-Reg 12 selectfont
         55 20 moveto (Sample) show
         grestore
         true
     } ifelse
   } bind
>> setpagedevice

To call the ps file, I am using this command line:

gs -dBATCH -dNOPAUSE -dAutoRotatePages=/None -sDEVICE=pdfwrite -sOutputFile=out.pdf stamp.ps -f in.pdf

I would like to know if you can use a similar .ps file to add an image, like a small logo. Thanks