If you have access to a PC. Go to the instagram feed, find the image, Right click, "copy image URL" just use the image tag on the UKSO comment window and paste the URL in there. As long as the image stays up on instagram it will stay here. For mobile, uhm, you could probably use the [img="place image URL here" tag. Close it off after the last " with another square bracket (I cant do it here because it will think its an image). Hope that makes a bit of sense?