I know I'm 1.5 years late but I figure I might as well answer this, maybe it'll help someone else!
I'm not sure if you mean LH employees in the US/other countries, or in Germany. I can only speak for the environment in Germany and I have to say that it's rather cold and professional - very German, I suppose. I'm a flight attendant and I'm always amazed when I fly with US airlines and the FAs there are very informal, even joking around on the intercom. We would NEVER be allowed to do that at LH. Everything has to be professional at all times. I feel like even our uniform standards are stricter than in the US - messy buns are a no-go.
It's funny cause during the layover everyone becomes best friends quickly - if we have a few days off we go partying together, tell each other really personal things, etc - so in that aspect it's a nice environment. the psychologists at the interview stage really did their job well and 95% of the people I work with get along great, there is no bitching or bullying, etc. BUT don't expect to become friends with your colleagues outside of work. you have fun on your layover but after that you might only see each other once a year, nobody really hangs out in their free time. but that's a German thing in general, people are very reserved, so I'm already happy that they at least open up during the layovers ;)