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.

Hi, 
I am getting this error  whille completing trailhead superbadge in a Trailhead Playground : 

Challenge Not yet complete... here's what's wrong:  
There was an unexpected error while verifying this challenge. 
Usually this is due to some pre-existing configuration or code in the challenge Org. 
We recommend using a new Developer Edition (DE) to check this challenge. 
If you're using a new DE and seeing this error, please post to the developer forums and reference error id: DLTSZJTA.

Can you please help.

Regards,
Debashis