Hello,
Since the last update, Minecraft on Xbox One seems to not recognize some icons in Global Resources for some packs.
I have noticed that by an user that used an application called MC Addons Manager which allows to add custom packs to Minecraft for Xbox One in Global resources. The icon of the pack is shown on the application, but once people goes to Global resources in Minecraft for Xbox One, the pack icon is shown as pink/black cubes (Missing icon).
I have joined photos to illustrate this issue. The first called "image0.jpg" is how the packs are showing in game, the second one called "image1.jpg" is an example of a pack on MC Addons Manager (As you can see, the icon is showing, whereas it doesn't in Minecraft), to finish, the "image2.jpg" is to show the content of the pack that has the issue (You can see the "pack_icon.png").
The issue seems to appear when users have made more than 6 packs globally (It's random, sometimes it appears after 12).
If you need any more precisions, don't hesitate to ask me. To reproduce the issue, you can download MC Addons Manager on Xbox One, install about 10 custom packs, click on "Use globally" button and then go to the game in Settings > Resource packs > Global Resources. You will see that the icons are "missing".
EDIT: Captures are from the concerned user.