Why is Select image Dialog empty when trying to populate ScriptableObject?

So I have created a scriptable object below:

 [CreateAssetMenu(fileName = "/Assets/ScriptableObjects/Cards/newCard")]
 public class CardData : ScriptableObject
 {
     public int ID;
     public string Name = "";
     public Image Image;
     public string Type = "";
     public int Dice = 0;
 }

When I go to the editor I create the object just fine, but when I go to populate the image value, the Select Image box is completely empty.

I have sprites in /Assets/Sprites/Cards folder and the assets are usable.

Why can't I see anything in the Select Image window?

Any help would be appreciated!

Jeff