Not sure what desktop you are using, but one application that can do it is xfce4-screenshooter
.
xfce4-screenshooter -f -d 10 -s /tmp/testshot.jpg
The above command will take a screenshot of the full screen with a 10 second delay and save the output to /tmp/testshot.jpg
There are more options that can be used.
$ xfce4-screenshooter --help
Usage:
xfce4-screenshooter [OPTION…]
Help Options:
-h, --help Show help options
--help-all Show all help options
--help-gtk Show GTK+ Options
Application Options:
-c, --clipboard Copy the screenshot to the clipboard
-d, --delay Delay in seconds before taking the screenshot
-f, --fullscreen Take a screenshot of the entire screen
-m, --mouse Display the mouse on the screenshot
--no-border Removes the window border from the screenshot
-o, --open Application to open the screenshot
-r, --region Select a region to be captured by clicking a point of the screen without releasing the mouse button, dragging your mouse to the other corner of the region, and releasing the mouse button.
-s, --save File path or directory where the screenshot will be saved, accepts png, jpg and bmp extensions
-i, --imgur Host the screenshot on Imgur, a free online image hosting service
-V, --version Version information
-w, --window Take a screenshot of the active window
--display=DISPLAY X display to use