I’d probably recommend the following;

  1. Add a custom state to the repeating group called ‘imageList’ which has a type of image and is a list.

  2. Create a workflow that triggers on page load and sets the state of that repeating group’s imageList to Do a search for Images:items until #3's Image where your search constraints are the Type contains Arbitrary text and Image isn't empty. You also want to add the random sorting there.

  3. For each image in the repeating group cell, it should be Repeating Group's imageList:item #Current Cell's index
    image

Should work fine but let me know.