I have collected these wallpapers for the last several years. Most have descriptive filenames. You'll find wallpapers in 52 categories:
225 Aircraft -- mostly modern military including the F22 Raptor
16 Artsy Fartsy
104 Beaches and coasts
42 Buildings -- many from Washington DC
627 Cars -- mostly classic cars from photos taken at car shows
13 Celebrities -- I shied away from these but ended up with a few
11 Churches -- inside and out
85 Comics -- South Park, Superman, Simpsons, Garfield.
9 Docks and Ports
71 Fantasy -- DND, Lord of the Rings type stuff
78 Flowers and Plants
23 Food and Fruit
134 Kincade -- Painter Thomas Kincade
49 Lakes, Ponds, and Rivers
26 Linux -- Penguins, etc.
102 Nautre -- photos that might not fit in the other categories from nature
78 Objects -- closeups of random items
24 Paintings and drawings
22 Roads and paths
127 Snow (and ice)
97 Star Trek
35 Urbia -- stuff you'd find in cities, but not cityscapes
50 War, soldiers, and war machines, aircraft carriers
35 Water creatures -- fish, whales, sharks, crocodiles
87 Weather -- lightning, stormfronts, clouds, tornadoes, etc.
I have maintained this collection for many years, and have run it through a duplicate checker. I cannot guarantee that there are no duplicates whatsoever, but I've made an effort to root them out.
I'm sure to some there are categories that are notably absent. I've tried to keep this work/church/kid safe, and there is no nudity, gore, or hate speech.
As I was collecting these, I rejected wallpapers probably in the tens of thousands. There were so many mountains, sunsets, beaches, flowers, and landscapes. I tried to keep only those that were either unique or of exceptional quality. One exception: the cars have not been carefully selected. I recently added most of these, and included almost all that I had, because I figure someone who wants a car as their wallpaper probably wants a specific car.
I very recently sorted these. Previously they were all in a single folder. I double checked my sorting, but there might be a few weird ones.
I like to use these for picture slideshow screen savers, too.