You can pass also the screen shot to save it on shared drive but if you wants to take a screen shot inside citrix then what i have tried was to use “The onscreen keyboard utility” .
By using window explorer and type On-Screen Keyboard and hit enter. then by using image click activity click on that particular window ,screenshot you wanna take. then click on “ctrl+alt+prtSC”. and paste it where you wanna save it.
sidenote - after opening the onscreen keyboard please maintain its state. and the window you wants to take screen shot. you can restore windows state by using short key as well.