This is the best place I've come across......

https://planetpixelemporium.com/planets.html

He's got all of the planets and some of the moons in the solar system all ready to wrap onto spheres.

As well as colour maps, there are bump maps which is really handy and for Earth there's even a cloud layer, specular layer and city lights layer.

The 1k images are free and adequate for but if you need a higher resolution you have to pay a small price for the 2k images.

Mat.