Hiya Lyra,
Welcome to Wizzley!
Photos wise, I either make my own using GIMP, plunder Pixabay or else look for other free to use pics on the internet.
On the whole though, I try to find ways to have products doubling as pictures to break up great walls of text. Take this as a random example, notice how the pictures are mostly Amazon book covers or artwork from there, Zazzle or AllPosters. The latter is particularly good for that, as they ARE images, but also for sale.
Ticks two boxes - pretty pages and potential commission.
Also, if you go onto an Amazon product page, sometimes people have uploaded extra pictures. I believe - and ChefKeem please do correct me if I'm wrong, as I'm forever telling people to do this... - that you can use those images too, as thumbnails and what not, as long as you're actually selling the product somewhere in your article. It's useful, as those pics are often much more colorful and eye-catching than the Product On A White Background standard template of the main image.
Tips for Noobs - You sound like you're already an experienced writer, so I don't know if the Wizzley 50 Article Challenge would be of interest to you. It was designed with absolute beginners in online writing in mind. Though, to be fair, everyone currently doing it is a veteran Wizzley writer. Including me, who started doing it at 600 articles... -.-
But it's open to all, if you fancied it, and each category already has, or soon will have, articles that have been written for Wizzley and approved by the admin team. They might serve as examples of what Wizzley admin finds acceptable.
Please don't be afraid to write here. WriterArtist has already pointed you towards the rules. It's a really friendly, laid-back place, once you find your groove. <3 And as you can see, there's always plenty of people to help you with that.