Optional MapSeries and DrawOrder parameters are added to the converter. They can be used in the same way as MapId parameter:
jnx2img input.jnx output.jnx "MapSeries=14"
jnx2img input.jnx output.jnx "DrawOrder=40"

If the parameters are not specified, MapSeries would be set to 36, and DrawOrder to 24.

The archive is available from the same link in the first post.