There are a 12 shortcuts listed on this Windows 8 Keyboard Shortucts page. (Three more than the other list).
Alt+Page Up
Move between applications from left to right
Alt+Page Down
Move between applications from right to left
Alt+Insert
Cycle through applications in the order that they were started
Alt+Home
Display the Start screen
Ctrl+Alt+Break
Switch between a window and full screen
Ctrl+Alt+End
Display the Windows Security dialogue box
Ctrl+Alt+Home
In full-screen mode, activate the connection bar
Alt+Delete
Display the system menu
Ctrl+Alt+minus (-) on the numeric keypad
Place a copy of the active window, within the client, on the Terminal server clipboard (provides the same functionality as pressing Alt+Print Screen on a local PC)
Ctrl+Alt+plus (+) on the numeric keypad
Place a copy of the entire client window area on the Terminal server clipboard (provides the same functionality as pressing Print Screen on a local PC)
Ctrl+Alt+Right arrow
“Tab” out of the Remote Desktop controls to a control in the host application (for example, a button or a text box). Useful when the Remote Desktop controls are embedded in another (host) application.
Ctrl+Alt+Left arrow
“Tab” out of the Remote Desktop controls to a control in the host application (for example, a button or a text box). Useful when the Remote Desktop controls are embedded in another (host) application.
You don't need an external keyboard, I think you're missing a trick here. Why not simply use the official recommended method?
Just press and hold the Windows hardware button and then press Volume Down (on the left side of the device).
This is analogous to pressing Win+PrtScr and will auto-save the screenshots in the Screenshots folder in the Pictures Library.
Best Answer
Windows 8 has several different views of the keyboard. Sounds like you just need to change to a different one. Here's the MS site for touch keyboards that I'll be explaining about.
In the bottom-right corner of the standard OSK (on-screen keyboard), there is an icon that looks like a keyboard for changing the style of keyboard. Notice the slightly different icon in the bottom-right corner of the second example OSK .
(My apologies if MS decides to change the link locations.)