Design Your Own Engagement Ring at Diamond Mansion. We will assist you at every step of the way to customize your dream unique engagement ring. Diamonds and Jewelry are plentiful in the Los Angeles Jewelry District, but no other company maintains a higher level of world-class customer service and satisfaction than Diamond Mansion. Few also are able to match the A+ Better Business Bureau rating. Diamond Mansion Co. has earned as a result of ensuring every customer is treated like family.