I also got that flickering on TW launchers (even on an S5 themed one). And actually, it's not a flickering, it is a stretched app icon (in the screenshot you atached it is Camera). I observed (at least in my case) that this happens when the RAM usage is above 700-750MB. try a custom ROM (after backing up, recommended) like SmartDroid Simple v7, NxTGen 13.1, ehich both have really good RAM usage (on Smartdroid v7 I got as low as 280, if i remember well. I posted the screenshot in that thread.
PHONE: Samsung Galaxy S3 Garnet Red 16GB (GT-I9300)
ROM : L-DROID 2.2.0
KERNEL: Stock for now
SD: 32GB SanDisk
BATTERY: Stock 2100mAh/ Extended 4800mAh