This tip is useful if you have a lot of image on your disk such as wallpapers, web images, etc. I would like to display a preview/thumbnail of these images on Finder because I don’t want to import them to iPhoto (since I prefer to use iPhoto only to manage personal photos).

To enable icon preview feature, go to view > Show View Options (keyboard shortcut: Apple-J). You can now tick on the show icon preview window. You can also choose to apply those options on All windows or This window only.

Now, your finder is like thumbnail view for folders in Windows Explorer and you don’t have to memorize file names anymore.