If I may. The product or service should uniquely speak for itself. White background slides can be both trendy, easy to make and easy to comprehend. And it tells a lot about the company and where they are in their startup journey. Logo’s can be stylized with a creative font. Not discrediting my service (I actually own a UI agency), and while I like the mission, it seems that decorating these pitches may give a false sense of security. Personally, I would go back to the founders, tell them to look their audience right in their eyes and tell their story, and it doesn't have to be a pretty one.