It might be a "bug" but I deleted some pictures by going to the post of the pictures I did not want, and edit, go advanced,
add, and then check the picture you were (supposed to download upload) and "remove it" That might delete that same same picture in the folder. as well as the post. Don't scream! if it does not work, as I have no pictures to "remove" from a post at this time, I am going from memory long past. I do not think in the normal course of events the pictures can be removed.
Belay that. I just tried it and it only removes the picture in the original post. No can do.