OK. In post #324991 Nagato has purple hair, purple eyes and nothing in her hair. In this post, Altair has silver hair, blue eyes and a hair tie.
The only thing that's similar is the hair style, but short hair is too generic to say that it's Nagato in this pic. It'd even be a stretch to say that it's Nagato cosplaying as Altair.
Besides, on the site we have...
uni said: >アサシンの絵はアサシンクリード?長門?? アサシンクリードです。長門とはあんまり関係ありません
"Is the `assassin' picture from Assassin's Creed? Or Nagato?" "It's Assassin's Creed. Not related to Nagato."