On Mac, if you want to find something it's Command-F. In Finder this opens up a dropdown, set Kind: Image, now you see all images in the folder, and nothing which is not an image. Command-A for select all, drag or right click to preview.
I explain it the way I do because I had never had occasion to try "let's find all the images in a folder of mixed file types" on Mac, so I started with "Find" and yeah. Quite simple indeed.
On Windows/Linux you would just open the first file which is a lot easier.