Hi Barb,
I don't believe you need explicit permission to use one of Playrix's image as a profile picture or on a page. Many co-ops have placed their images on FB and other website hosts (weebly, etc.) for a long time. As long as you're not claiming it as your own creation, it should be fine.
If you're still worried, however, you can place a disclaimer somewhere like:
"All images are copyrighted to Playrix. We claim no credit and will promptly remove them if asked."
You can then contact Township Support in-game. Response time is always slow (but esp so for non-game related inquiries).