I find it really annoying how watermarked stock images dominate Google Image results for some searches, and are ubiquitous in all of them. I also have a personal objection to Google indexing stock photos, given that A. many of the smaller stock image companies are basically copyright trolls (they don't so much make money from licensing their images as by suing people for violating their licenses), and B. Getty images sued Google for caching its images and forced Google to stop providing a link to images. Google was how they got most of their users at that point, but they still forced Google and all its users to provide them revenue on their terms.
After the Getty thing, I determined that neither Google nor Bing has any option to filter out stock photos. Helpful people all over the internet will note that you can filter images by license, and I generally already do that if I'm going to reuse and/or modify an image (I will use images I don't have the license for if I can't find a free one, but never, ever from stock image sites), but if I just want to see what something looks like, I'd still prefer not to look at watermarked stock photos.
Well, after another fun round of "can I find an image of this without a watermark?" I decided to see if there's
any image search engine that will let you exclude stock photos. I can't find any—there's a lot of people out there who share my hatred of stock photos, though with a variety of reasons, but evidently not enough for any search company to cater to us—but I did discover that
there's an addon for Chrome and Firefox which filters stock images out of Google Image searches. I don't know how, but hallelujah it appears to work!