I have some experience on stilts - here are some ideas.
Partially related: I would definitely recommend a cane or staff, to help navigate the crowds and hills at Dragoncon - it would be all too easy to get bumped by another con attendee and lose balance, and taking a spill off the stilts would probably ruin the rest of the con for both of you. Make a sturdy cane or pole with the skeletal hand on one end, for photos he can hold it horizontally under the cloak with the finger pointing out to the side and it'll look like a super-long arm; then for walking he can use it for balance and safety.
He can bend a bit to get lower, bending at the waist or crouching a bit, or leaning to the side, but he's not going to get all the way down to 5'3". This is easier if he can lean on the cane.
If you have room, you'll probably want to stand in front of his cloak and do a "big" pose such as with arm or sword raised. That way, a portrait-orientation image will still show both of you.
You can also stand closer to the camera, with him looking over you in the background. The perspective difference will make you look larger by comparison - for example, if you are 10 feet from the camera and he is 20 feet from the camera, he will be small in the background. This won't work very well in a crowded area like the Marriott but should work well for any photo shoots where you have the room to move around and position yourselves.
Do some test shots with the help of a friend - even in partial costumes, even just with a smartphone camera - so you can get an idea of how you look together.
Last edited by nathancarter : 08-03-2015 at 10:18 AM.