Photo search optimization

I have been toying for photo optimization for the past year for a car wrapping company (a very visual company). I have named photos such as "car-wrap-city.jpg", "truck-wrap-city.jpg" (various local cities used) and posting them on all kinds of social media and photo sharing platforms but only a few photos from Twitter and Facebook appear in search. The top photos have always been from the website which I do not have access to. The other top competitor photos are directly from their website as well.



So is there a point to sharing photos on social media/photo sharing platforms for photo optimization purposes? It seems like the website is the primary location to be dabbling with. Perhaps the photo sharing platforms are ideal for general search (not photo)?



Also I have read alt tag detail is critical. Where can alt tag information be inserted other than website photos?



Thanks,

L