I may have discovered a solution to the red & white checkerboard leaderhead background problem. It also appears to have greatly reduced the frequency of Civ-5 game crashes, too.
Background: Was able to play Civ-5 G&K without any crashes, using no mods, on my Windows XP machine with an Nvidia GeForce 9500GT videocard. However, playing G&K with even just one mod (any kind) would cause frequent crashing and cause the red & white checkerboard backgrounds to appear. Using more mods simply caused the problems to occur more often. (Did notice that just before each game crash, there would be a distinct CLICK sound from my computer.)
After unsuccessfully trying numerous suggestions from others on changing settings in Civ-5, settings in Windows, settings on my video card, and even upgrading to an Nvidia GTX550 Ti video card, I was about ready to throw in the towel.
Fortunately did one last Google search and found some helpful tips on the squidoo.com website. I did the following three things, and after about 400 more game turns played, have not experienced any more checkerboards. Also, the game crashes have dropped off enormously (even while using more than 20 mods) and the previous CLICK sound has gone away. Since I simultaneously did all three of the following fixes, am not sure which one did the trick, but at least one of them has surely helped.
1. Changed my Civ-5 game setting to run in windowed mode, instead of full screen.
2. Updated my VC++ libraries, by going into C:\Program Files\Steam\Steamapps\Common\sid meier's civilization v\VCRedist\ and then running vcredist_x86.exe
3. Updated my DirectX, by going into C:\Program Files\Steam\Steamapps\Common\sid meier's civilization v\DirectX and then running DXSetup.exe
Please try these possible fixes and report back if they work for you too.