Finally figured out that you can do so by overriding the formatter type in the app.config file like so:
<add type="Microsoft.Practices.EnterpriseLibrary.Logging.Formatters.TextFormatter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
template="[{timestamp(local)}] {category},{machine},{message}"
name="Text Formatter" />
The difficulty was in finding the template keywords for the data I was interested in adding to the log.