Sgt_Kickaxe - 6:56 pm on Oct 16, 2013 (gmt 0)
I've reported this before. A picture of a brick, another of a duck, one of a frog and another of a hubcap were all blocked by safesearch on my site a while back, along with 50 others.
There isn't a single even remotely risky image or word on the site but that didn't matter. An image reconsideration request and email solved nothing. The image file names and alt text are not the problem as these are benign as well.
Best guess: A competitor is reporting images which gets them labeled unsafe, even if they aren't.