Many clients at OW decide to use a "Look and Feel" which is a replication of the header and footer of their current company domain. This allows for the OW instance to feel on-brand without having to rely on an active project manager for the build. 

There are also those clients that want to take things a step farther and perform their own Look and Feels or simple designs into the platform. Below you will find a video on the process of building a custom theme along with the basic files needed to begin

Theme Files
 

https://vimeo.com/411200599