No deep dark secret. In fact, jes, I'm glad you asked. My methods are many.
Today, I had nothing specific in mind, which is often the case. I have a variety of ways for dealing with "nothing in mind." Today, I entered "mammals" in google. I could have looked at the photos provided for mammals, but I didn't. I looked at some of the Web sites that give info about mammals. I found a site that gave an alphabetical list of mammals. I clicked on addax, a mammal I never heard of. I entered "addax photos" on google, and looked at the photos. I looked at a bunch of pictures, many were of addaxes in zoos or dead addaxes with their heads being held by the hunters who shot them. I'm disinclined to show animals in zoos, and I'm even more disinclined to show pics of dead animals. I kept going from page to page looking for the right addax photo. The photos got farther and farther afield from addaxes. I stumbled upon a very strange looking mammal with a lot of horns. I checked what it was and entered "four-horned ram" in google. Found one I liked. Voila.
This kind of accident is not uncommon in my searches. Looking for one thing; find another.
I wanted something completely different for the second photo. Don't know why. I just did. Went to google and entered "sea." Then I paused. Sea what? Star? Slug? Let's try "fan." Liked what I saw.
Here's one of my addax rejects:
Sometimes I'll enter something like "snakes madagascar" or "birds fiji" and see what I get. Sometimes I'm looking for something specific.
Suppose I find something with the word tiger in it. On a whim, I'll then enter, "tiger butterfly" or "tigerfish" without knowing whether such things exist. Sometimes they do, and the end up here.
I could go on, but I think you get the general idea.