{
	"Title": "First Aider",
	"Type": 1,
	"Rows": 2,
	"AssetId": 250250,
	"Active": 1
}

Here is a list of the available Types...

'Rows' refers to 'Number of Rows' when creating a new Text Field, it's not applicable to the other Types.

AssetID is the ID of the image that you would like to associate to the new additional field.