All pictures....whether they be on your skydrive or on your phone, are stored in the Pictures hub. No pictures are stored in the Office hub. If you're looking for a picture, don't look in the Office hub. They won't be there. Office hub is for documents, spreadsheets and OneNote notes. Pictures hub is for.....well......pictures.
All pictures that you upload to your Skydrive via a computer, will be accessible through the Pictures hub on your phone. It's not actually stored on your phone, but is accessible (it's stored on Skydrive). If you want something stored locally on your phone, simply access the picture through the Pictures hub, and "save" the picture. This will store a copy of it locally on your phone. Otherwise, all pics are on Skydrive, and fully accessible on your phone (Pictures hub).
All good?