For scripted image operations, the major player is ImageMagick, which is free. Have look at their
command line processing page for an idea of what it can do. It can convert multiple files at once. You could add the relevant commands to the script before running the replicator.
If you're looking for a replicator, and it's an all-Windows setup, then
Microsoft's SyncToy is fine, and now includes a good command line / scripting version.