VS Code CloudFormation Linter uses cfn-lint to lint your CloudFormation templates.
Uses cfn-lint to parse and show issues with CloudFormation templates
For example if there is an image subfolder under your extension project workspace:
Requires cfn-lint to be installed:
More information about cfn-lint can be found here
The code for this plugin can be found on GitHub at awslabs/aws-cfn-lint-visual-studio-code