You can display posts/custom post types associated with a certain custom field using the following attributes.

• meta_key – Custom field key.
• meta_value  – Custom field value.
• meta_value_num – Custom field value number
• meta_compare – Operator to test the meta_value. Possible values are ‘=’, ‘!=’, ‘>’, ‘>=’, ‘<‘, ‘<=’, ‘LIKE’, ‘NOT LIKE’, ‘IN’, ‘NOT IN’, ‘BETWEEN’, ‘NOT BETWEEN’, ‘NOT EXISTS’, ‘REGEXP’, ‘NOT REGEXP’ or ‘RLIKE’. Default value is ‘=’.

Examples:

[wcp-carousel id="767" meta_key="color"]

Above shortcode will display posts where the custom field key is color, regardless of the custom field value.

[wcp-carousel id="767" meta_value="blue"]

Above shortcode will display posts where the custom field value is blue, regardless of the custom field key.

[wcp-carousel id="767" meta_value="blue" meta_key="color" meta_compare="!="]

Above shortcode will display posts where the custom field key is color and the custom field value IS NOT blue.

[wcp-carousel id="767" meta_key="price" meta_value="22" meta_compare="<=" post_type="product"]

Above shortcode will display Products where the custom field key is price and the custom field value that is LESS THAN OR EQUAL TO 22.
By using the ‘meta_value’ parameter the value 99 will be considered greater than 100 as the data are stored as ‘strings’, not ‘numbers’. For number comparison use ‘meta_value_num’.