Same here on my 6s+ in the last few days, every new update from now on the icon on the store is now grey. If I tap on that app to go the the the page where you can buy/get it, the icon is missing entirely.
If I do a search though instead and go to the same page, the big icon is there. Apple has screwed something up badly.
There is also an issue with viewing the iTunes store on the PC (Windows 10). If I view the store the entire page is corrupted and the layout completely screwed up.
This is definitely not my end as I installed a fresh copy of iTunes 12.3 on a fresh copy of Windows 10 in VMware workstation and the layout is screwed up exactly the same.
Apple really needs to fix this quickly.
UPDATE - There is a discussion on the screwed up layout on the Apple forums. Seems the affect OS X and Windows, good going Apple.
https://discussions.apple.com/thread/7273948