What you can talk about? 
Why don’t you host an Open Space “Unconference”?
I have a write up about the first Belgium Meetup I hosted with the open space format and it was quite a success. You can totally do this on an internal conference also.
=> First Belgian-Leuven MoT Meetup! 11 October - #4 by kristof
As Callum said: Soft drinks, Snacks are a must have!
Workshops are quite popular and don’t mention the word “training” you could label it as “Teambuilding” otherwise some people might see it as a negative.