if your app is going to store user's images and files, you should consider storing these into a DB as LOB data instead of using the file system, so if one day you decide to cluster your app, it can scale.
Update- if you don't want to store blobs, you can have the best of both worlds storing file metadata in the db. So you'd have freedom to add tags to your files without the worry about how these files must be organized physically in the file system