By using my FTP program I uploaded the 2 additional files rainydaypuddles_01 and rainydaypuddles_02 to images/pyramage.

When I now go into IH the two files are shown correctly named as if they should work perfectly, however only one is still showing on the site.
Your base image is a png as is your first additional image

Your second additional image is a jpg
One can not mix file types as Zen Cart keys of the base image name/type for these

rainydaypuddles.png
rainydaypuddles_01.png
rainydaypuddles_02.jpg

Change/convert the rainydaypuddles_02.jpg to rainydaypuddles_02.png and your issue will vanish