Generally, photos from previous owners aren't deleted, but become part of the record of the specimen. If you've kept the same MinID (which you should), I believe the way it works is that your new photo becomes the new parent (or you assign the new photo as the parent), and any additional photos you upload plus any photos from previous owners all become its child photos.

It's quite likely that your new photo will be from a slightly different angle or direction (or a very different angle or direction), or use slightly different lighting (or very different lighting), be from slightly closer or further way, or have a different background. Any or all these potential differences offer the possibility that new or unappreciated visual features of your sample will become noticeable, so having all the old photos still available for comparison is always useful and adds to the richness of the specimen record.