THIS "FIX" WORKED FOR ME...
Alright, this touchwiz issue seems to be a common samsung flaw across multiple devices. It appears on my samsung mega 6.3 for example, after certain applications like "zedge" start up the issue because the app has the ability to change the wallpaper or manipulate the homescreen with custom downloaded images from zedge. However, the fix of choosing, settings/home screen mode/easy (or) standard view mode (depending on whichever is opposite of what mode you're already in, then going back in and switching back again) usually fixes this bug.
Though just recently, I noticed the issue was back and was relentless. It was driving me crazy and every time I'd hit the home screen button from an app I was in, it would ask me to reselect a default view mode. I tried clearing touchwiz cache and data, uninstalled apps I thought might be the culprit, and all to no avail. I was actually even considering a factory reset until I just by chance noticed how odd it was that this "bug" started occurring around same exact time that my google search app had automatically updated and the icon changed in appearance on my phone. I went to settings/application manager/all/google search, and uninstalled updates back to original factory app setting. No more touchwiz popup dialog! ^^
Just make sure you go into google play store/settings, and uncheck automatically download updates before any of this to ensure it doesnt update again right after you've uninstalled the updates.