Yosemite corrupted texture in Mission Control
Based on your specifications I am guessing that you are using a MacBook Pro with Retina Display. I have heard about glitches with ones that have a dedicated GPU because OS X actually used both the integrated and the dedicated side by side. To fix this problem you are probably going to want to reset your SMC (System Management Controller) which controls these things.

Step 1 : Shut down your MacBook.

Step 2 : Connect the MagSafe power adapter into your MacBook. If it’s already connected, leave as is.

Step 3 : Press Shift + Control + Option + Power keys at the same time.

Step 4 : Release all the keys from the keyboard.

Step 5 :  Press the power button to start your MacBook.