Have your CEO just sit in during lunch hours. This will help close a certain gap and create connection.
Invite all new teammembers in their second week to a one hour meet & great and have a few standard games/questions set up to get some fresh insides but also to meet the CEO as early as possible, again to close the gap.
Make sure the CEO has an open office - walk in Q&A time scheduled. Even when no one shows up, it should remain on calendar and pointed out to people as a podium to talk about initiatives etc.