The 'Other Storage' issue in Windows Phone is something many are unhappy with. The bug consists of taking up large amounts of space on any Windows Phone 8 device under the category of 'Other'. No one really knows why this happens, until today. A developer bu the name of Kévin Gosse has dug deeper into the matter and has found that the bug is caused by two system files.
When taking photos on Windows Phone, the OS saves a copy of it into the camera roll, and another copy into MediaLibrary.SavePicture and MediaLibrary.SavePictureToCameraRoll, both system files within Windows Phone 8. This happens when saving an image into the pictures app, which is what Windows Phone does automatically when taking photos using the build in camera.
Kévin Gosse created a small app to test whether this was true, and his findings confirm that these two system files save photos more than once in isolated storage. What's interesting is that the bug only happens with .JPG files, other file types like .PNG's are not affected.
So, this is why the 'Other' section of your Windows Phones memory is taken up. It's the photos you're taking, along with other temporary files which aren't being deleted by the system. Microsoft are aware of 'Other Storage' issue and have claimed to be looking into it, however this claim was made months ago so hopes have sunk low.