By default OS X does not show icons with thumbnail previews. For a large image/photo collection, thumbnail preview is very helpful. What is thumbnail preview? It is where the icon is changed to a preview of the actual image/video.
I am a fan of thumbnail previews. I was happy to find that OS X makes this an easy thing to do.
Here is what it looks like when off.
1. Open Finder to the Folder than contains the icons you want to change to Thumbnails
2. Press CMD-J to open the icon dialog window
3. Select Show Icon Preview
4. You may want to adjust your icon or text size here. You can watch all these changes in real time in your open finder folder.
5. Also check if you want the previews to be shown in just this window or in all windows. This is the top-most selection in the dialog box
6. Close your dialog box when you are finished making your selections
Here is the same folder with thumbnail previews enabled.