[CustomEditor(typeof(TonScript))]
public class TonScriptEditor : Editor
{
    public override void OnInspectorGUI()
    {
        DrawDefaultInspector();

        TonScript script = (TonScript)target;

        if (script.mySprite != null)
        {
            Texture2D texture = script.mySprite.texture;

            Rect rect = GUILayoutUtility.GetRect(100, 100, GUILayout.ExpandWidth(false));
            EditorGUI.DrawPreviewTexture(rect, texture);
        }
    }
}