monline

You can select a number of images in Finder, then right-click and select Slideshow. This will start Preview in slideshow mode, but there's a limitation: you'll see only the first hundred images from what you selected. However if you select "Open" (or "Open with Preview" if it's not your default app for images) in Finder, then you'll see all selected images in Preview. Of course now you've to manually start the slideshow. One more thing: sometimes Preview messes up the order of images in the right pane. In this case you just have to right-click one of the images in the pane and select the name of the ordering type again (probably this will be the default "name").