This very easy tutorial will show you how to add [ ] around your score in the scoreboard overlay like in the mini scoreboard overlay. This only works for games where deathmatch is set to >= 1. This is very effective for online games; like taking a screen shot of your score while in intermission.

In sbar.c/Sbar_DeathmatchOverlay, find this if statement

if (k == cl.viewentity - 1)	Draw_Character ( x - 8, y, 12);

change this to

if (k == cl.viewentity - 1) {

	//	Draw_Character ( x - 8, y, 12);

	Draw_Character ( x, y, 16);		// katua - draw [ ] around our score in the

	Draw_Character ( x + 32, y, 17);    	// scoreboard overlay

}

Compile and then join a server and press the key +showscores is bound to. Take a look at your score. This also works with +teamscores in CRMod.
That's it!