Creating a TOC for an InDesign pub with pictures instead of type

Using pdf's or images as text will make your ebook less accessible for a large group of readers and maybe even inaccessible for some readers.

Readers with visual disabilities are very diverse in what they need to adjust the text so they can read it. They might change the font, size, color, font weight or all of them. They might enlarge the page to more than 400%, even up to 800% or more which can be a problem when the text is an image.

Maybe they are only able to see a small part of the page or only the middle part or everything but the middle part or no colors. The possibillities are endless and so are their solutions.

Ebooks are great because the reader can change the font in many ways. Please don't use images of text to retain a font in an ebook.

An alt text as @Laura Brady suggested won't help. Above mentioned readers often don't use a screen reader so the alt text will not be available to them.

I understand your wish to keep what you've created, I would want the same thing, but I've seen enough people struggling with inaccessible digital documents not to want this anymore.

You cannot create a TOC without live type. You can put the type in white and .01em if you want. Or you could add display:none; to the CSS of the chapter headers you want to be invisible. 

One note: be sure to add alt text to the PDFs in InDesign so that that type isn't invisible to print-disabled readers. 

We need way more information here. I, for one, have no idea what you're talking about so please back up and provide some details.