I have a multi-language store and try to choose the best URL key for categories. Also note that it can be set only for all store views, for a multi-language store it is a problematic point because the URL key for categories is a global value.
Also I try to add the main key word in the URL path because the store sells just one type of products - paintings. I can use this key word in the URL key in all store languages, but maybe it is not such a good deal - for example painting-painture. Or should I add the key word in the end of the URL key for each product? Another solution is to keep it language independent and don't use at all the main key word in the path but just the artist name instead. What do you think about?
Edit: Take a look to this question for an alternative method.