The Nokia Design Team has opened an account on audio sharing service SoundCloud in order to provide easier access to Nokia related sounds. Collections of various Nokia sounds are available from the standard sounds (ringtone, alerts, and sound effects), to the music used in Nokia adverts, and a collection of regional ringtones.

All the sounds can be played back in the browser and many of the original files are also available for downloaded. If desired, the downloaded files can be added to a Windows Phone 8 device as custom ringtones, but do note that many of the sounds are already included on Nokia's Lumia smartphones as part of the standard Nokia collection.

Here's the profile description from the Nokia Design Team's SoundCloud page:

Hello! Welcome to the official account of the Nokia Design Team. We will be updating this page with lots of great sounds for you to enjoy, from device sounds such as the latest Core Brand Sounds (including the new and improved Nokia Tune!), to a selection of music tracks that have been used for advertising our devices.

Here's an embed showcasing the Nokia Core Sounds 2013, including an updated version of the Nokia Tune, the Nokia Startup sound, standard Nokia Message tone, and more:

But our favourite sound is the Cat (2014 Edition) ringtone, a more purrfect version of the standard Cat tone included in our current Lumia devices. One can only hope the new version will be included as part of the standard ringtone collection in future Nokia devices:

Adding a custom ringtone to Windows Phone 8

Custom ringtones can be added to Windows Phone 8 and will appear in the "custom" collection / section when specifying a ringtone in the ringtones+sounds settings module. In order for a ringtone to appear in this "custom" section it must be added to the Ringtones folder:

1. Connect your Windows Phone to a PC
2. Browse to your phone using File Explorer (look under portable devices and double clock on the phone folder)
3. Open the Ringtones folder (top level folder)
4. Copy the sounds file from your PC into the Ringtones folder

In some cases it may be necessary to convert the audio file to a format support by Windows Phone (e.g. MP3). It's worth noting that some WAV files will not work because Windows Phone supports only a limit number of WAV encoding / codecs.

Unfortunately it is not possible to customise tone sounds (e.g. new text / IM, new voicemail, and new email alerts/tones) on Windows Phone devices.