This one is a quick fix. Many people I've worked with so far hate how they don't see the thumbnails for their pictures any longer. Here's the fast fix.
1. Open "This PC"
2. Click VIEW and which brings up the ribbon.
3. On the far right click OPTIONS and select "Change Folder and Search Options"
4. Click the VIEW tab.
5. Uncheck the "Always show icons, never thumbnails" box.
Once you Apply this change you'll see all of your pictures begin to change back to thumbnails like they have been in previous versions of Windows.
I'm not sure why they opted to make this change but this will fix it.