choose not to use them.
They're typically too slow and they don't understand consulting and business concepts in a way that helps the presentation. They mistake aesthetic design as being meaningful improvements to a presentation. We're kidding about firing them, but let them focus on branding, and only use them when your content and storyline are already rock-solid.
High quality presentations are about communicating the business story in an effective way. They are about becoming landmarks and anchors within the minds of your consulting clients, where they associate key images with important concepts, and use the images to describe the concepts to their peers. Good presentations are a refection of the firm and their thought process. They gain legs -nay wings!- in the organization, speeding through meetings and e-mail as independent, permanent agents of the consultant's ideas, even when the consultant has long left the building. While good looking visual design is part of a professional impression, these other objectives are just so, so, so much more important.