You could also create a character for each language I suppose. The animation method that Sebastian mentioned would be less work though. Forcing which animation frame to play is as simple as...
ActiveAnimations["name"].AnimationFirstFrame = 1
ActiveAnimations["name"].AnimationLastFrame = 1
... though you can make the code even shorter if you use my set animation frame workflow function which is available on the script index page on the wiki.
As to where you should add this line of code... it should be added inside of the first frame of each animation & should be wrapped by some if language = ? queries. Alternatively you could use display object text actions, which would be a nicer method as you can specify text for all available languages for each one. I don't know how you would handle the positioning of them though as you would need to use Lua script to force them into position. Also text is always displayed on top of the screen, so you wouldn't be able to overlay any other images above the text.