Yesterday Google posted new  image placement a policy  for adsense publisher.  This statment released via official adsense blog   , and the point is you cannot place associated images  near adsense ads associated.  Example, if your site topic about dog  you cannot  place  dog  images near your adsense ads, even if you place a small space or a line between the images and ads, this is not allowed. Try using non related images with dog topic.

for full policy you can read it here , official adsense blog