Where is the data stored for the metro app - Photos

Currently the app shows "placeholder" images for all of my photos - but no longer shows the images themselves unless I select an individual photo.

I want to essentially reset the app entirely, so it starts its life over.

Ideas?  Thx.

Update - I somehow managed to clear the old data - I think by removing all folders under settings.

Would still like to know where the data is - perhaps in the super-secret "AppsRepository" folder LOL