I do not know what specific features of scala you'd like to see in a game lib. My gut-feel says it is better to use a well known and fully functional java engine than a new scala one. Using java libs out of the box is one of the "specific features" of scala ;-).
A while back, I wrote a small game in Scala using the GTGE. I can really recommend it. The scala source code is on launchpad if you'd like to take a look before using it.