360° panorama

You can create such 360° panorama images by using special hardware that outputs "Equirectangular projection" images. If you just want to experiment, there are quite a few sites that offer free downloads, e.g: Depositphotos or Photopin or Dreamstime. These images always have 2:1 aspect ratio, and need to have at least 4096px horizontal resolution to avoid pixelated output.