epub: does using images instead of chapter titles produce a valid epub file?

Hi, there, I was planning a new ebook with my illustrator, and I stumbled upon something which I couldn't figure out. 

My illustrator wants to use graphics (i.e., a jpeg file) to serve as the title at the beginning of the chapter. 

How do you do that in the docbook way? 

In a previous thread, Bob said that you could use an empty title element to suppress the chapter title. 
http://markmail.org/message/gkokzarw6zxo3fiq?q=suppress+chapter+title+list:org.oasis-open.lists.docbook-apps

But I would need to have a way for the chapter title to appear in the TOC (and also in the epub navigation document? Does anyone know?) 

How can I use a graphic for a chapter heading and still have a nice looking TOC/epub navigation document? 

This is actually a common use case in ebook production; often an illustrator will want to embellish a chapter title and maybe integrate it with another graphic. So I'd like a robust solution to this kind of problem (hopefully one already exists!) 

Robert  

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Robert Nagle
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