Some don't allow commercial use and may consider the paywall commercial use.

Some require links to the CC licence and if you don't include that link, they may sue, like this example: https://medium.com/illumination/students-get-5000-legal-demand-for-using-cc-image-on-a-blog-6cba99b58d88

Some require the photographer's name to be included and if you don't include that, they may sue, like this example: https://medium.com/illumination/blogger-who-made-6-is-sued-for-150-000-over-creative-commons-image-a1fa4f33cb9c

Some include ShareALike, which confuses me a little, so I just try to avoid it. There are different interpretations around monetising an image that has ShareALike conditions attached. There's an example of that here, although the defendant won the case (see 'even if you win, you lose'): https://medium.com/illumination/people-are-being-sued-for-using-creative-commons-images-adc5c8ba1491

Some demand a link back to the photographer's website. That was missed on this example: https://medium.com/illumination/students-get-5000-legal-demand-for-using-cc-image-on-a-blog-6cba99b58d88

Basically, they can make up any terms they want to on Wikimedia Commons, so you have to be very careful to be compliant.