Go on the Lush website and look at what they do and what their aims are.
They aren't the same as Body Shop or anywhere else that I have been. The staff know about their products - care about what they do. They are against animal testing. They seem to have a sense of humour-fun. Look at the way they write on their products.

If you can draw, maybe a cartoony type picture showing you, with a big smile, helping a customer?
Or a short poem - not too serious, about you, and how you think you will fit in with the shop's ethics.

Or try a product - like a bath bomb and describe the experience of using it - and big it up a bit.

Don't leave it too long or the job will have gone.