Move through images in a folder with Preview.app
If you are just skimming the pictures do this:

Instead of opening a picture in Preview.app by double-clicking it, just press space to preview the picture when selected in Finder.

This way you can still use the arrow keys to navigate between the pictures. 


&#x2191; and &#x2193; in list view
&#x2191;,&#x2193;,&#x2190; and &#x2192; in icon view


You can still open the picture in Preview.app when needed (top right corner).