The devs have made the huorn pets "stand out a bit more" with the patch and hinted that there are now other pets that can be obtained. The big change here is that pets will live on the client instead of the server, allowing players to turn off others' cosmetic pet visuals if so desired to improve graphical performance. Also, the lil' pets can now be renamed.
Other changes with 13.1 include a fix for Quickbeam's quieting quests (say that five times fast!), an auto-fellowship feature for friends, an option to automatically add tasks to the quest tracker, and a new inventory sort button.