Most vendors have done tons of weddings, and likely have tons of photos & examples to show you. So, always ask your vendors to show you samples of their work so you can get a better understanding of their style.

Most florists will do a mock up bouquet and centerpiece based on your requests, and you can make any adjustments from there.
As for your DJ/Entertainment, you can ask to see videos or listen to samples of their previous work.
Other vendors you can ask for photos/samples from are: photographers, videographers, wedding cake bakers, hairstylists, makeup artists, caterers, event decorators, venues, and even wedding planners.

http://africanweddingbliss..com/2016/04/always-ask-to-see-vendors-work.html