Moodboards are not designs or wireframes as such, and are not - strictly speaking - an IA deliverable at all. Really, they're a way for visual designers to elicit and explore emotional reactions to things like colour, imagery, illustration and opther possible factors in some future design.
Moodboards have a vital role to play during Origination, and are heavily used when developing visual identities and brands. I should add that they're a great fun and very effective tool during workshops, where you might allow a group to create their own moodboards - carboard, magazines, scissors, felt-tip pens and glue - to explore particular questions about a project or brand, e.g. How to you feel about X?
That's about all I know about moodboards really, or rather, all that I feel is relevant here. I'm not a visual designer, after all.
Am I repeating myself?