We at a classified websites got banned from Google Images results. And we know why.You see, on our website, ads are subject to expiration. When ads expire we redirect the expired ad page with 301 to its closest listing page. Google started indexing our images but as soon as their ads get expired, people who get to the site from the View image option lands on a redirection.Google then, banned us on Google results for images.We know what to do to fix this. We need to return a 404 instead of a redirection. But what about the SEO juice that passes from the expired ads to our listing pages? 
Redirecting expired images to a category page got us a Google penalty, but won't a 404 lose lots of SEO juice?
seo;redirects;images;google image search