The best you can do is make a suggestion for multiple pet sizes in the CS Help, Suggestions and Problems forum board, but I'm pretty sure it's been suggested before and turned down. Honestly most of the pets are reasonably sized for what CS is formatted for, just apparently not forum signatures for forums that have a height limit

I'm part of CS staff (albeit not an admin by any means, haha) and could try to have a word with the owner about it but I doubt it would become a thing. It really isn't a problem on CS's forums itself so not a concern of CS. The best we can do here is try to choose the smaller types of pets on CS for our signatures that Lupineleigh posted, or shrink the images of our pets down ourselves and upload them then hyperlink them to the actual pet's page. Unfortunately that would mean if you dress them up and change the dress up, the image would not update until you saved and edited it yourself again. This isn't against CS's rules- by the way- changing the pets image size. As long as you don't remove the watermark or edit pets (like make fake items on them or make your own version of pets over the same outline), you should be fine. You can shrink them, flip them, or whatever, if you'd like.