Smooth paved outdoor areas are a nightmare for many new VR photographers. The lack of control points between images can make it difficult to align images well enough without having grout joints running into tiles or tiles becoming distorted in the final panorama.
Bird droppings, discarded chewing gum or other blemishes can be of great help as control points when going through the stitching process.
Try to see the bright side when facing a stitching challenge, even the pair of sneakers or a plastic bag hanging off a powerline can help to get those much needed control points in the sky. If you want to get rid of blemishes in the final output, use Gimp or Photoshop to clean up the marks instead of removing valuable control points with a mop and bucket. To be on the safe side, never try to remove things from powerlines to get a good shot.