Thank you Alik, I tried it and...
In a more "general" usage it’s working fine (except in the chunk I had to name tv [+show-in-list-as+] to make it work)...
...Unfortunately for me it’s doesn’t, sorry I forgot to tell all the story :
In a child doc (pagetitle of doc="document-name") containing an image for example : the image is in a tv named "postimage".
So now following your idea :
in the tv "show-in-list-as" I had to write something like :
<div class="doc-type-image">
...
<img title="[+pagetitle+]" src="[+postimage+]">
...
</div>
And that doesn’t work :
the result in the source of the final HTML is :
<img src="" title="document-name"/>
A you see, MODx fills ok the document variable "document-name", but doesn’t fill the tv "postimage"

I think it’s a "recursive" problem

I think...
Maybe there is a solution to make it work with PHx, but I don’t know how it works...