I would suggest installing the application
shutter for taking screenshots. Should be in the repos for Debian. The main site for the app is here: http://shutter-project.org/.
It allows you to configure the PrtScr button so that it captures the screen within Shutter, rather than use GNOME's method for capturing. It also allows you to capture regions, whole windows, the entire desktop, right click dialogs etc. It also allows for annotating images by adding arrows, circles, blurring out text etc.
I use it every day and it's by far the best screen capturing tool I've found in my many years of using Linux. Take a look at the screenshot gallery on the project's website along with the various screencasts showing it in action:
Making it the default for PrtScr
If you'd like to make this change you can do so under GNOME's Settings dialog, specifically the Keyboard applet's Shortcut's tab.
Will get you to the Settings dialog. From there click on the Keyboard applet, then the Shortcut tab. From here you'll notice one of the choices on the left, it should say Screenshots.
From here you can see what keyboard shortcuts are present on your system, and Shutter can act as a drop in replacement for them by grabbing the full screen, active window, region, etc. But to override them you'll have to add entries under the Custom Shortcuts like so:
Shutter can be called via command line to do the screen shooting so simply changing the action when one of the buttons is pressed, to the corresponding
shutter command, to map other types of actions. From
shutter's usage page:
$ shutter --help
Capture Mode Options:
Capture an area of the screen. Providing X,Y,WIDTH,HEIGHT is
Capture the entire screen.
Select a window to capture. Providing a NAME_PATTERN (Perl-style
regex) ist optional.
Capture the current active window.
Capture a section. You will be able to select any child window
by moving the mouse over it.
Capture a menu.
Capture a tooltip.
Capture a webpage. Providing an URL ist optional.
Redo last screenshot.
So with that mapping in place you can now hit the PrtScr button and get a full screen grab like so: