High quality, detailed images of planets on web
The best NASA images of planets are not from the Hubble Space Telescope; they are from the spacecraft that flew by or went into orbit around them. For Uranus and Neptune, this means Voyager 2; for Pluto, this means New Horizons. For Jupiter, this means primarily Voyagers 1 and 2, and especially Galileo and Juno; for Saturn, Voyagers 1 and 2 and (especially) Cassini.

If you google for "[planet-name] planet gallery", you should get some pretty good images that way; also try adding the name of a relevant spacecraft (if you're stuck, check the Wikipedia page for each planet to learn which spacecraft visited them). A few NASA web pages:


https://photojournal.jpl.nasa.gov/mission/Viking
https://solarsystem.nasa.gov/planets/saturn/galleries
https://solarsystem.nasa.gov/planets/neptune/galleries
https://solarsystem.nasa.gov/planets/dwarf-planets/pluto/galleries


and so forth. (Note that Uranus, even when seen by Voyager 2, is pretty featureless and boring, at least at visible wavelengths.)

You might also try searching at the Astronomy Picture of the Day site. (Not all of those are necessarily public domain, thoug.)