I think somebody needs to define "not safe for work".
Our corporate proxy does not allow us to download pictures of beer, for example.
For the longest time, my AVATAR (a bottle of Das Echte Schwaben Brau) was technically NOT SAFE FOR WORK.
Again, if your company is THAT uptight that an embedded graphic that you didn't even click on could be a potential problem for you, DON'T SURF CHIEFSPLANET WITH A COMPANY COMPUTER.
Quite frankly, if you work for a Fortune 500 publicly-traded company, surfing the Planet - SFW or not - is against company policy.