After playing through Fallout 3 on the Xbox 360 and got up to the Mothership Zeta DLC on the PC, you can imagine that I have every achievement, these images seem to suggest there are secret ones, maybe for a future version..?
[Update] Apologies, it appears the owner of the images has removed from the Flickr account.
Although some may look familiar, it seems some of them are secret/unused achievement icons…
Or maybe not since by Blackopps42( Que Pasa?!?!? ) created them on Flickr.