Cathedral Wall Backdrop, basic frame

So my Imperial Chapel build is currently on hiatus, probably until I figure out a good way to either make the corner pillars a lot sturdier or something suitable to replace them with. I still have a big pile of foamcore around, so I decided to start on another, more limited project.
What I'm building is pretty much just one wall with a window and possibly some small doors, and intended to be used as a backdrop for my miniature photos. I'm planning to add a faint lightsource behind the window, so in addition to adding to the background, it should also improve the lighting a bit, too.

Here's the basic frame of the wall, approximately where it'll be once it's finished. I had to take the picture from further away to get the whole wall in frame, and a little from the side to show the flying buttresses.
I'm keeping it simple for now, with just a couple of small buttresses and one large window frame. I intend to add a small section of wall under the window, to make it look less like a glass door.
Once the basic architecture is done, I'm going to start adding decorative elements. I won't spoil what sort of decoration I'll add, in part because I'm not completely sure myself yet, but it will take a lot of pomp to make the building fit with the general theme of 40k Imperial architecture.