We were able to customize our Help Center with just a bit of CSS/Google-foo. I was able to add our trademark image as a faded background to our support articles.
In Help Center's CSS, I looked for the background, found it and referenced our custom image.
The net result was the following:
background-position: bottom right;}
You will need to upload the image to your Help Center. To do so, see Uploading and using your own assets.
This turned out to be much simpler than the "figure out how to override our CSS" method of customization which has flummoxed me with similar site designs.
Watchman Monitoring, Inc.