Sharing Yu-Gi-Oh! card ideas
Konami has general contact information for their offices. However, I highly doubt that they will accept unsolicited card suggestions. There are a couple of reasons for that:


They are already paying people to design cards, and they have a lot more experience.
If they were to accept fan-submitted cards, you would not be the only person submitting them. Konami would have to pay people to sift through all of the thousands of submissions.
Fan-submitted cards might have rights or legal issues. Do you own the card? Does Konami own the card? What happens if you submit a card and they radically change it? Do you have any say over the final outcome?
If Konami is like most TCG companies, they already have hundreds if not thousands of cards that they would love to publish someday (they plan out new sets well over a year in advance too). They have no need for half a dozen cards from a fan.


Konami has to date released 16 fan-made cards. Out of those, 15 of them were winners of contests that Konami specifically held, usually "draw a monster" contests open only to children. The last one, Tyler the Great Warrior, was a Make a Wish Foundation wish for a 14-year-old cancer patient (who ultimately survived). As best I can tell, all of these fan-submissions were only for monster designs and not for card stats.

Given this, I think your chances are practically zero for being able to show a card to Konami. Your best bet is to participate in one of these fan contests they have, or if you are an adult, convince a child to draw a monster that matches your design.