Filtering animated pornography gifs/videos/images/ads (most directed at children)

I have a network that teenage boys access, and I continue to block individual sites, but I can't seem to keep up with all of them.  We have web filtering enabled, but when a gif/video has animated characters "texting on screen in the image" sexual content, nothing seems to catch it.

Any ideas?  I can provide examples, but I would prefer to do that in a PM (due to appropriateness on the site).

Thanks!