@pehja,
Yes. That makes sense. I just tested that functionality again and I didn’t have any trouble with it. However, you do have to be careful about which post an image is actually attached to.
In order to check what post an image is attached to, you will need to find that image in the media library and check to see what is listed in the ‘Uploaded To’ column. If the images you put in the new page were pulled from the image library, then they were probably attached to another post already.
Another way to do the same thing is to use the shortcode on the page and then pass a comma separated list of attachment IDs that you don’t want to be in the mix when selecting random images; like this:
[mpress_image_refresh not="54, 67, 118"]
This will show all the images attached to the current page except those whose ids you just passed in.