Set 1st post image as “featured”

Hello !

I use the WPPA [photo random] shortcode to add a random photo in a large amount of posts. I really appreciated that you added this feature in an earlier version. Thank you!

And I’m trying to make a post grid page from these posts, using other plugins (like Post Grid or Content Views), where each post of the grid is represented by the thumbnail of the first image of the post. A little bit like in this example

But this kind of plugins (Post Grid…) need either a Featured image set in the post or an image added inside the post content, to be able to use it as a source of the post grid thumbnail.
The problem is that WPPA shortcodes are not recognized as images by these plugins. So the resulating post grid appears without any thumbnail, even though the posts themselves have an image in them, thanks to WPPA [photo random] shortcode.

I could add featured image to the posts one by one. But it would take ages. And since the pictures are managed by WPPA, they don’t appear in the default WordPress media library that opens when you want to select a featured image.

I could also use a plugin that automatically sets the first image of the post content as the featured image (like Easy Add Thumbnail). But again, these plugins don’t see WPPA shortcodes as an image.

Another idea is to use a plugin that adds random Featured image in bulk (like Quick Featured Images).
In this case I wouldn’t even add an image in the posts content since my posts would be illustrated by the featured image, which can even be resized in the post content by my theme.
But the problem is that this plugin can’t add unique random images. It will reuse them randomly contrary to WPPA which can be set to use the random photos only once (setting in Table IX-L-7). And I want each image to be used only once.

I tried many things, but now I feel a bit out of ideas to achieve what I want.

tl;dr

To sum up, I’m trying to :
– add random unique images (either featured or in the post content) to a large amount of posts
– create thumbnails post grids from any taxonomy (e.g. categories) from these posts.

Can you help me to achieve that please? ??

Maybe if there was a way to set the an image added into a post as the Featured image, in WPPA options, would be a solution.

Thanks for reading !