I've always hired a company to do my choreography and music. This year I am contemplating tweaking my own choreography and hiring a producer to mix/record my I1 freestyle. Depending, I might have the company I usually use do a freestyle for a clients horse at 2nd (or 3rd level if he wants to learn changes this winter).
No costumes as I've always done them in sanctioned competitions and demos where formal attire is required/warranted.
So far I've done music from old western TV shows and movies for a Quarter Horse, rock music with my old mare, classical with the schoolmaster I used to ride and upbeat/80s pop with my current horse. Here's a link to our most recent freestyle choreography/music: