The other files may not be from your camera. Different apps you use may be leaving files on the device and without clearing out the cache for each of them, there would be no way to remove them.
You can search pretty much any folder/space on the phone when it is connected to the computer via USB cord. If it is actual photos you took or downloaded, then you can move those.
If it is the other that I mentioned above, then you need to go into your phones 'settings' and then 'apps', go to 'all' and locate the apps that could be the cause (say browsers or facebook, etc.) then tap that app and then tap "Clear Cache". This will remove the saved files for that app. BE SURE you are OK with clearing them for any app before you do this as once it is done, those files are gone.
Worst case, if none of this resolves it, you may have to do a full "Hard Reset" of the phone. But I would save that for last as that will wipe all data off the phone and restore only the original phone stuff. All your personal stuff would be gone.