You can leave them displayed for a while, but it is bacteria, and will continue to grow, and eventually break down. Then you can change it out later with the pictures.

If you open the petrie dishes, you are opening up bacteria, etc.. At this point I would wear gloves and a mask. You can do scrapings and look under a microscope or you can get a newer digital version microscope for looking at larger items, it’s more handheld, or use a high power magnifying glass.