I can talk about how I built New Year tweet visualization (http://tomasp.net/blog/2015/happy-new-year-tweets/), which covers server-side, asynchronous programming and agent-based concurrency (and it has a nice visualization!) This is a bit more advanced talk.
I can talk about building web servers with Suave.io and web development (how to build your own “WhatsApp”)
I can talk more about data science and FsLab (analysing data with F#), but Evelina will cover some of that
I could also do a more introductory talk “10 easy ways of getting started with F#” which is great for audience where people have not been doing much F# before