Next time you have a problem, please state WHAT the problem is - don't just throw in a screenshot and assume it'll be obvious to everyone. I had to look at it for a good while before I realised what the issue was, because I thought you were talking about something wrong with the map.
Changing the z value will not make a difference, because pictures are displayed in a different viewport. However, I would expect the picture to also be light, BECAUSE they are in a different viewport than the map, and tints apply to the map and not pictures. So ... next question is, what OTHER scripts are you using? How are you making the map darker?