tag-posts plugin & adding thumbnails

tag-posts plugin:

I'm trying to add a thumbnail of the first image that's used in the post. I've found a couple different codes but the problem I'm having is, it's not showing the correct images.

Some codes will find the image from the first article listed and use it as the thumbnail for each of the following posts.

Some codes seem to be finding the last uploaded image and using THAT over and over.

Thank you for any help you may be able to provide.