I 'really' love the entire "King In Yellow" plot point and it will be the focus of one of the final games at our con this year.
But, IMHO, the character/figure itself could vary
wildly 
I am entirely unfamiliar with the background where Uncle Mike got this from (or if he *really is* just that ill...), so I had no idea what era this "play" was set in, so who can say what "The King In Yellow" looks like other than I assume he is wearing yellow as well as a crown of some sort...

I took mine from an old horror clix figure with minimal wash/paint. Not bad for a $1 figure and a quick wash/paint and rebase. I grew to like it more and more as it took shape from the batch of clix I got.
GG's King In Yellow----------
As for terrain... I would jump on the graveyard or farmhouse. Both will yield many good options for fights/investigations.