I don't think the term is very accurate, it might be a nicer and less "pretentious" way of putting it but I don't think the words are descriptive enough. I wouldn't use the word celebration to describe a lot of art and imagination is not a very specific word either, while most art is imaginative in its execution not all is from the imagination.
I would perhaps say something more like "an imaginative expression of intellect and emotion". In my opinion the two things which drive the majority of art are intellect and emotion, and I think expression is an important term when describing art. I don't think there is a simple definition to describe all art though, the term means different things to different people.