Add ImageById to provide details on an image id
diff --git a/interfaces.go b/interfaces.go
index 8d5887c..6786d39 100644
--- a/interfaces.go
+++ b/interfaces.go
@@ -145,6 +145,9 @@
 	// returns full details for each image, if available.
 	ListImages() ([]Image, error)
 
+	// ImageById yields details about a specific image.
+	ImageById(id string) (*Image, error)
+
 	// Flavors
 
 	// ListFlavors yields the list of available system flavors.  This function