Well, I think now I don't need any plugin. Google answered my prayers with Twitter post to Feedburner. Thanks for the concern.
And yes if you want to expand the plugin, yes it should update twitter each time when a photo is published (not uploaded). You can include options for hashtags, custom text in before or after the tweet and url shortening.
And this question is for Zenphoto developers, why does ZP publishes date in description field of feed? It should use date field of rss for that.