Recently we were given the task to promote the upcomong conference at our university, so I wrote the twitter post: "getting excited for this year´s conference themed Terrorism" Is it gramatically correct?
English has a long history of using nouns as verbs—verbing nouns, as it were.
If the conference had terrorism as its theme, it is unobjectionable to say that it was "themed Terrorism."
For more illumination, see this ELU blog article from a few years ago, titled The Give That Keeps On Gifting.
(And do notice the verbing of "title" in the previous sentence.)