What can I add to my mood board?
Whatever you want! Have some fun with it. What is the focus of your website? Are you selling something? Find some ads that have a similar look and feel to what you want to convey. Feel free to also include stock photos, other websites, color schemes, illustrations, ads, and really anything that you feel would inspire the theme of your website!
The important thing to accomplish with the mood board is to have something you can show your client to quickly communicate the visual feel and direction of the project.