Large Tile on Win 8 App

I am trying to update my game on Win 8 and struggling a bit with the start screen icons. When I deploy to a surface 2 pro to test, on the start screen the small, medium and wide icons display fine, but the large tile icon is blank (Black). I’m confused, its been a while since I tried to build and deploy for win 8 apps, but when I check my released game on the actual production win 8 store it doesn’t have a large icon, so presumably somewhere it can be disabled. I’ve checked every image in the windows store player settings, they are all there, so not sure what to do next. I can see images in the visual studio solution under Assets, there is

LargeTile-Scale-80.png
LargeTile-Scale-100.png
LargeTile-Scale-140.png
LargeTile-Scale-180.png

and they all contain my logo. I am assuming my update will fail verification without this - Microsoft checks the tile images. I am using unity 4.6.5f1 .

Has any else encountered this?
Is there a way to turn off the large tile?
Any other suggestions?

Ian

OK, this turns out to be an easy one, in visual studio when I select “edit manifest”, there are little red crosses over the corner of two of my large tile images (not sure how I missed that before) - mouse-over tells me that they are too large in size. Turns out the images have a size limit of 200k, which is fair enough, If I use photoshop’s “save for web”, I can easily get that size down with no obvious change in quality and then the tile works.