There is a vast amount of amateur and professional photographs posted on https://www.flickr.com/. That is where I get a great majority of some the highest quality of photos posted in this thread.
Hubble Palette North America Nebula, shot with a Rokinon 135mm lens and ZWO ASI533mm Pro, 12nm Astronomik filters. Roughly 3 hours of integration per filter, 1.5 minute subs for the Oiii, 3 minute subs for the H-alpha and Sii, shot at f2.8 and Gain 100.