The order of the images. Changing the preview image.

Hi. How do I change the order of the images? I have to delete it and upload again, if I accidentally threw out the wrong image, it's pretty weird. Well, or at least it would be great to be able to change the preview image.

If you edit an image set/post there is an option to rearrange the order. Just drag the one you want to be in the preview in the first place (and make sure to save the changes) and that's it.