Developers are really into Roman Nurik's new live wallpaper app, Muzei. A ton of extensions are already available in Google Play, some of which have neat tricks up their sleeves (see part 1 here). Here's the best stuff we've found so far in no particular order.
Muzei Music Extension
This extension plugs into your music player and changes the background to match the album art of the current track. It comes from the developer of the popular Shuttle music player. The music extension includes settings to restrict data usage to WiFi only and to control the artwork resolution (which comes from Last.fm). It should work with almost all music apps – I tested it with Google Play Music and it worked great. Some apps might require you fiddle with the AVRCP/Bluetooth settings for the app to send the required song information.
The power of hashtags in your live wallpaper – just fill in some Google+ hashtags in the settings and this app pulls in the images associated with it. It comes with #photography and #longexposure selected, but you can pick anything you want. It's more of a hit or miss selection of content, but you get a good variety. Muzei Hash also includes refresh rate and connection settings.
Unsplash for Muzei
Unsplash is a photoblog with a ton of lovely images. They look great as backgrounds, but the app doesn't have any settings. It just updates whenever a new photo is added to Unsplash, which happens 10 times per day.
Cast for Muzei
The Chromecast sure has some pretty backgrounds these days, and now you can get them in Muzei. This extension pulls from the same feed Google uses for the Chromecast's backgrounds. There are no settings in this app, though. It just updates when the feed does.
Dropzei for Muzei
This extension plugs right into your Dropbox account to pull in wallpaper images. You can add multiple folders and control the refresh interval. There are no settings for data usage as far as I can see.
Muzei – deviantART
If you're a fan of deviantART, this is the extension for you. It lets you specify the update interval, NSFW preference, mobile data usage, and the feed it pulls from. Selecting the feed might be a little weird as it uses the same syntax as deviantART itself. For example, in:photography/nature loads images from Photography > Animals, Plants & Nature.
Just a few days and already we have a bunch of cool stuff in the Muzei ecosystem. Like last time, Muzei and all of the extensions featured here are completely free.