My Nyancat - NyanDog Scoreboard. I have it for a long time. Its UNDETECTED ! You can change the icon to whatever you want, you just have to edit icon_cfgfactory_1.iwi and icon_cfgfactory_2.iwi like its a normal skin.

SO HOW TO INSTALL 

1. Open nyan.rar with winrar
2. Copy all the files from Zone/english to Your Call of Duty folder/zone/yourlang/ (eg. E:\Program Files (x86)\Activision\Call of Duty 4 - Modern Warfare\zone\english)
3. Open localized_yourlang_iw00.iwd (located in cod4 folder/main) and place the .iwi's from images (located in .rar) to the images folder located into the .iwd (You can open .iwd files with winrar or packscape)
4. Open your CFG with notepad and go the the line of your scoreboard bind.
5. Add the follow part in that line: g_teamicon_allies icon_cfgfactory_1; g_teamicon_axis icon_cfgfactory_2 It will look like this: (My Scoreboard bind) "bind TAB "+scores; g_teamname_axis ^9NYANDOG!?;g_teamname_allies ^8NYANCAT!?;g_teamicon_allies icon_cfgfactory_1; g_teamicon_axis icon_cfgfactory_2;g_ScoresColor_Axis 0.586 0.797 1 1;g_ScoresColor_Allies 1 0.613 1 1;g_TeamColor_Axis 0.586 0.797 1 1;g_TeamColor_Allies 1 0.613 1 1""
6. Save the .CFG, Open COD4 and enjoy !

FAQ 

Q: On custom maps my icon is not working 
A: This works for Default maps only, if you want to have it on custom map you have to copy one of the .ff files and edit the existing one of that custom map.

Q: I get kicked by Punkbuster for "iw_00.iwd is different from the server".
A: You have placed the .iwi files in the wrong .iwd