Typically a mood board helps to put together thoughts you are not able to puts in words, take many, then select the best and see the common patterns: playing with words, rhymes, etc.
You can also look at your competition, and see how they do it, do you think it is good, or do you want to differentiate? This very much depends on the industry (e.g., in banking as new entrants you want to show trust and might want to look quite conventional).
Contributors: Emna Everard from Kazidomi