Mammillaria lloydii is a species which isn't universally accepted as a good species. We have a number of images in the A-Z section.
I'm looking for more though, either in cultivation or in habitat, which must have either a field number or a specific location, and ideally both.
This is for my own personal research, but should this ever get to become something I'd write up, then all contributions will get full attribution.
If anyone has such images, then please send me a pm, and I will send you an email address to which you can safely send the image(s).