Two things. First use a free metadata editor like Mp3Tag (http://www.mp3tag.de/en/) or Media Monkey (http://www.mediamonkey.com/) to put track/title information/album art into the media file(s). Second I found that I have to label the file name using numbers to get it to list properly in some DLNA clients. For example: 01 Hells Bells.mp3, 02 Shoot To Thrill.mp3, 03 What Do You Do For Money Honey.mp3, etc.
Also see the following thread that has a sort of unofficial best practices/suggestion guide for using the Twonky media server embedded within the My Cloud:
https://community.wd.com/t/faq-twonky-dlna-media-server-setup-use/95373
