Changeable Thumbnail Image?

Can there be a way where, after you submit your post, you can not only edit the text, but also the image attached to it?

Earlier I uploaded this image to the Concepts board, but no thumbnail displays, and I feel like that sort of thing would limit the visibility of the post. I wanted to change it to something else in the future, perhaps, but it looks like I'd just have to delete the entire post and start over if I want a different image source.

I've also had problems with my Blood Moon Karma post, where I took critique and edited the image, but the thumbnail wouldn't refresh, so people kept commenting about things wrong with the old image, rather than critiquing the newer version.

That's just a couple of my recent problems, but I've seen a few other weird happenings with the thumbnails, and it would be nice to see them become editable.