Images are not indexing as they are in temporary ads and when the ads expired we redirect the ad image to the parent category

[divar]

As we are a classified ads site, our ads expire after some time,and we redirect 301 the ad post page to the parent category And images urls in the ad page is redirected to, so they are not getting index in google image..what is the best solution for getting image index in this situation: 301 redirect images Keep images And so more?