This is fanart of a warriorcats adoptable that later sold.
https://ko-fi.com/s/7bb378df00

As an aside the artist Raavenna has a number of (quality imo) designs going on her kofi shop for real cheap, warriorcats included, and you can even commission a grid adoptable if you're gunning for a customizable bigcat design. Commissioned her to make bigcat grid adopt designs to sell as adoptables before.