Make second image in shuffle mode (first "back" image) random, instead
of loading the first two images in sequence. The first image remains
non-random because it determines the image dimensions for the rest of
the run, which you probably want to be the same each time, even if your
image collection is mixed-size.
Also upped optimization settings in the project file, though no real
performance difference either way is apparent from casual inspection.
Considered putting in a fps monitor, but it doesn't seem worth the
effort.