The Preview app on your Mac can do more than just show PDFs. It is also a great image viewer. It even lets you sort your images for viewing inside the app. While it's no iPhoto replacement, it's an easy way to get some images together for a quick and easy viewing.
Here's how to do it:
1. Open a folder with some pictures on your MAC.
2. Select some pics and then control click and choose 'Open With - Preview'.
3. Now Preview will open all of those images and show them in the sidebar.
Note: If the sidebar isn't showing, in Preview, go to the View Menu and choose 'Show Sidebar'.
4. You may notice that the images are out of sequence. this is easy to fix. At the bottom of the sidebar is a round cog. Click on it and choose 'SORT BY' and then select the option you want. - Name, Path, Size, Keyword, Date, or Kind. I typically find Sort by Name works to get them in the right order, since most camera name the images with incremental numbers.