Cats are fine. As are a lot of the non-pleo images in the gallery. Anything in moderation is fine. A lot of the non-pleo images help members to get to know each other better. SO don't worry about posting pictures of your cats, wombats, or western seagulls (you know who you are....).
But the problem is increased as a lot of those "non-pleo" albums tend to also be full of images that do not belong to the person who posted them.
If I see a really funny youtube video, I would post a link here on this site that points to youtube. That is all fine and good. Likewise, if I see a really cute or funny image on another site, I can easily post a link here and show the picture here without a problem. But when I see a cute or funny image on another site, save it to my hard drive, then upload it to my album here, that's stealing and is a copyright violation, and could put this site in jeopardy. (Based on his other posts, I'm sure watergazer is all too familiar with issues like this from other online communities has has been involved with.)
Uploading images to the gallery that don't relate to pleo (or to the member), and are already available elsewhere on the internet, is usually not necessary anyway. the [ img ] and [ /img ] tags allow you to display images stored just about anywhere on the internet without having to upload them to the gallery.