Design Patents are a form of patent that covers the nonfunctional creative and design aspects of a product. They are valid and can be used to exclude others from practicing your invented design. However, design patents do not cover the useful or functional aspects of your product design.
Although you can combine a utility and a design patent, this would allow you to protect both the useful and aesthetically pleasing aspects of your invention. This may allow you to protect the functionality and cool look of your invention as you can see from https://www.tekrevue.com/inventhelp-tech-invention-off-the-ground/ post. Apple and Steve Jobs were masters of using this form of layered intellectual property protection to take advantage of trends and consumer preferences.
However, you could still add more layers of intellectual property protection by registering the product packaging as a trade dress and/or copyrights on the original aspects of your product design. This allows for the creation of a portfolio of IP rights to give you a greater advantage in the market place.
This form of tiered IP protection strategy also helps against the expiration of IP rights. For example, design patents last for 14 years, utility patents are good for 20 years, copyrights last for the life of the author plus 70 years, and trade dress rights are not limited by time as explained in https://steemit.com/inventions/@businesses/inventhelp-protecting-ideas-and-inventions article.