Waffle is an easy-to-use but helpful and powerful image utility that helps you create photo mosaics directly from your Mac. This application works with a wide variety of image formats and offers you high-quality results within a few minutes.
The first thing you need to do is to select the target photo from your local drives. Then, you choose either individual pictures or an image folder, set up the grid options, and click the Render button.
The app supports various image formats (even RAW images are supported), offers clear output settings, and allows you to preview the results before exporting them to your local directories. What's more, you can share the output files directly from the app's main screen via Facebook or Flickr account.
The only aspect I don't like about this Mac tool is that it supports only three output formats: PNG, JPEG, and JPEG-2000.
All in all, Waffle provides you with quality results and you don't need any graphic design experience in order to get the job done. Plus, the application comes with a very reasonable price. Hence, I can't find any reason why you shouldn't try it.