yeah that is the alpha channel for photoshop, if you get the .tga plug in for photoshop (you can get it at www.adobe.com) it will turn black so u can see where the alpha channel is so no more checkered pattern
I actually prefer the checkered pattern, so it doesn't blend in with any of the rest of the skin, and you can more easily see the shading Blizzard has put over the teamcolour (without messing with alpha layers).