There has been a discussion on this in the fora. Here are some of the things you can do:
1. Avoid storing a lot of photos in your phone. It seems that the cache for the photos (e.g. such as the one being displayed in the Photo Hub tile) is kept in the "Others" section. In my past experiments, transferring a lot of photos to my PC from my phone also reduced the "Others" size.
2. DisablePhoto Auto-upload. Photos uploaded to OneDrive are effectively duplicated in the cache (since there would be a cache for the photo in your phone and for the photo in OneDrive) to be displayed in the albums in the Hub. I've also experimented on this in the past.
3. Go to Temporary Files and tap on "Delete". Even if "Temporary Files" is an entirely different storage category, it has been found that deleting the temporary files also deletes some of the "Others" Storage.
4. Check that all your photos and media files are being recognized by the phone.
4.1. In case you transferred photos from your PC directly to your SD Card, you might observe that some, if not all, of those photos will not appear in the Photo Hub - they are still under the Others category, waiting to be recognized.
4.2. Other media formats that are not recognized by the phone will also fall under the Others category.
Let us know which of these are applicable to you and which ones worked.