http://sequentialx.com But it misses a zoom option to fit to the window. LilyView and Xee are two good paid options. All will let you open a picture or folder and cycle through all of the pics in the folder. This is something that Preview.app definitely needs.
You can also do a lot with Quick Look. Try selecting multiple images in Finder > press Spacebar > then press CMD-Enter. But it'll block you from doing something else in Finder. You also can't selectively delete some and keep the rest. Or even tag some you need.