I acutally applied for a Design patent. About 10 years ago. Just was not refined enough, was trying to get the info together they wanted, never panned out for me. The patent? Was for a car that ran on battieries but had a smaller onboard engine to recharge while driving. Think Chevy Volt. MY idea 10 years ago.
The first patent for such a thing was applied for in ~1905 by Henri Pieper. HIS idea, 110 years ago ;) (just funnin').
Getting a patent isn't tough, but you do need to be an expert on the subject to be successful. I've been involved in at least two dozen in the past 5 years. All prior art (things similar to, or which have inspired your design) need to be disclosed. This includes searching the patent office for similar items, looking for products and designs which are similar and then arguing why your idea is novel vs the other ideas.
That's the crux, it has to be novel. Not obvious, not an improvement (you can patent an improvement, but it's not a standalone thing, you'll still be liable to respect the patent of the original item being improved) and these days the patent office wants it to be more concrete. IE: buildable.
Then there's design vs utility patent. A utility patent is far more useful, since it patents a thing. A design patent only patents a design, or aesthetic, or appearance of a thing. Basically, you could put a design patent on the shape of a fender, but you wouldn't be owed royalties by everyone who makes a fender - only a person who makes a fender that is close in design/shape/appearance to your fender.