Remove Set() overhead for read-only view model.  Change cover image generation to on-demand to avoid generating "full" image until it's needed.
Switch the default Expander style/trigger so that games can be seen in the design view in VS.  I'm still not 100% fond of needing to run code for design-time data, but the alternative (using DesignData XAML) requires making various view model values publically settable, which seems a worse offense.