Wrong approach.
1. Assemble a folder of images.
2. Open QuickTime 7 Pro (if you don't have this, you can still get it, it costs $30 if I remember correctly)
3. Set the image sequence timing, point to folder, voila a QT movie.
4. Download one of the dozens and dozens of programs that offer to run a QT movie as your wallpaper.
If for some reason you can't run QT7 Pro, there are a number of apps in the Mac App Store that can assembled a series of images for you (look for "stop motion" as a search term). Then as mentioned above just toss the completed movie into a "movie wallpaper" app and that's all you need.
As mentioned above, you will probably be pretty unhappy with the results. Because of the very high resolution of your Mac's screen, making a movie that will fill it will be a very large one. Running it continuously will tax your processors and your fans pretty hard. You can get an idea of this by simply running any "movie wallpaper" type app with a sample movie (I have one that puts a fireplace on my screens for wintertime). As you'll see, even images optimized for this purpose will tax your machine in the same way watching an HD movie will (because that is exactly what you are doing).