Yeah, there's pretty much no way James is sitting for a proper portrait in any kind of throne/chair... aside from maybe Sirius's motorcycle. :P At least with the tree I get to do the antlers thing.

Sirius is in a number of Minor cards such as 5 of Pents and 6 of Swords, and referenced (and possibly pictured) in a few more like Ace of Swords and 5 of Cups. He actually has more appearances than most characters besides the Trio!