Thunar's "send to" menu option can be easily extended using desktop entry files. All we need is to create a new desktop file in
~/.local/share/Thunar/sendto/ for each destination. The desktop file has a
MimeType field which allows you to control on which file types the "send to" option will appear. If you omit the
MimeType the option will appear for all types.
The example bellow is a option to send my sketches to Picasa. It appears only for PNG images and uses a shell script that I wrote and is in
$PATH. You can use it as a boilerplate for your own.
# sketchupload.desktop - Send to Picasa [Desktop Entry] Type=Application Version=1.0 Encoding=UTF-8 TryExec=sketchupload.sh Exec=sketchupload.sh %F Icon=picasa-16 Name=Send to Picasa MimeType=image/png;