I decided to update the picture in the background to take out the discontinuity between the repeated tiles. So I took a new photo of a pinstripe ginger leaf (Alpinia formosana). I don't seem to have saved the cropped version of the original photo. It would have looked more or less like this:
I then flipped the image horizontally, vertically and both horizontally and vertically. Putting those four images together makes a tile that should tesselate perfectly.
Here is a mosaic approximately the shape of my screen: