This component works but does not validate and gives the following error message:
Step not yet complete... here's what's wrong: 
The CSS does not contain a reference to the background image 
Note: you may run into errors if you've skipped previous steps.

I installed both the Opp Alert Coponent and the ContactsToday Component from the Trailhead Module "Working with Custom Lightning Components". However, they are not available to add as components in the Lightning App Builder. I've tried uninstalling an reinstalling, with no luck. The "Custom Components" section in Lightning App Builder shows 0.

Any help would be appreciated - I've had nothing but technical difficulties with this module and I want to earn that darn badge already!