I think the problem here is that you are trying to get vim, which expects to run in a terminal, to recognize a CTRL-SHIFT sequence. While it's possible for X to recognize such combinations, applications that run in a terminal (or, these days, a terminal emulator) cannot. This is because, historically, terminals could only send and receive seven- or eight-bit sequences of ASCII data across a serial connection (though this could include "escape sequences" that position the cursor, scroll or delete lines, change color and other helpful effects).

There are 32 "Control Codes" in the ASCII character set, including the familiar CTRL-A through CTRL-Z. But there are no corresponding ASCII codes for "CTRL-SHIFT" A through Z. Now, gnome-terminal itself can recognize these codes (CTRL-SHIFT-V, for instance, will paste text from the clipboard), but vim will not be able to have direct access to it.

Of course, it may be possible (I don't know) for a terminal emulator to be set up to convert CTRL-SHIFT key presses to an escape sequence which can then be recognized by a vim mapping.

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UPDATE

You might be interested in gvim, which is a graphical version of vim that runs as an X program rather than a terminal program. Maybe gvim will be able to understand CTRL-SHIFT codes?

There is a simple workaround for what you need.

1. First you will have to install xdotool .

2. Then launch the Keyboard configuration gnome-control-center keyboard:
   (Go to Shortcuts → Custom shortcuts)

   

3. Click on "+" and add a name like "Paste into terminal" and the command

   xdotool key --clearmodifiers ctrl+shift+v
   

   

4. Then choose Shift+Insert as the key binding:

   

Because of a bug, you will have to logout and log back in so the shortcut can take effect.