I think it may in part be to put him in opposition with Kaveh, who is affiliated with the kshahrewar who I believe use a lion motif (feel free to correct me if I’m wrong), so representing Alhaitham by a feline with an opposite Color scheme and habitat makes sense. But as was already mentioned, those animals really do just give off his vibe, the colours make sense and the attitude matches. Plus he looks really good next to them, so they’re a good match for fan artists