If you want to take screenshot of the remote host, you can use the xwd utility if you have access to running DISPLAY:
DISPLAY=:0.0 xwd -root -out screen.xwd
It takes the whole screen capture (with -root arguments) and stores it in a special x-window dump file. You can look this file with several utilities like gimp. Xwd files takes too much space. For example, it is about 7,5 MB for 1680x1050 display. But you can compress it using gzip with the compress ratio of 30:1 or even more.