Uh oh! I have no photos to display!
If you just activated the Image Wall plugin, then I am most likely still working on processing your images and generating a random order. Get a cup of tea and check back in an hour. If this error is still here, then go to the 'Settings -> Image Wall' admin screen and switch to the 'Calculation' image order method. If you've done so and still see this message? Then please contact me and let me know that you have a problem, and I will take a look at it!