Wax seals look great when done properly. However, they may change the weight enough to increase the cost of mailing. Also important to note is that wax seals can't survive the fast sorting normal process of the USPS. You need to ask for hand stamping.
If you happen to like the President, you can send an invitation to the White House. The first family probably won't show up, or even personally see your invite-- but the correspondence office will send you a nice reply. Your tax dollars already paid for this, so you may as well enjoy the citizenship perk.
Send it at least 6 weeks in advance.
There are other non-W places you can send invitations to if these collections interest you.