As the subject reads, the "Showcase" theme does not work correctly out of the box if you have renamed the wp-content directory.
I am using the security plugin, "Better WP Security." In order to harden WordPress security, this plugin suggests that the wp-content directory be renamed. I have done this for most of my WordPress installs and until today have had no problems that I am aware of.
If you rename "wp-content" you will need to specify the folder location in the theme settings.