What about a little more 'period' touch - like a simple parchment to add a neutral texture to the white background and a more 'King James Bible' font for the text (unless it is more of a 'celtic' church - like the 3rd century or Saint Patrick era).
From a pure 'technical' standpoint, it needs a graphic scale.
What's it's intended purpose?
Archaeological drawings have one technical standard and function, while a handout for people visiting a tourist site serves a very different purpose.
It's for a conservation plan, but its not to scale at all (its a site sketch I did while inspecting the ruins).
I can't really add a parchment effect because it is for a report on the ruins, and it would look a bit mad.
But it seems a shame to restrict ones-self to black and white. Historically these church plans were always black and white due to printing, but nowadays I can use any colour I want. I want it to look crisp and modern and simple.
OK, that sounds like a worthwhile goal.
First the walls ... the rock probably has a real color (or at least a dominant color) so what if the walls were 'rock' colored ... either outlined in black to make them stand out or all one solid color.
Windows ... for Architecture glass is often rendered blue so many people will instinctively associate blue with sky/open/glass making it a good candidate for 'windows'
Doors ... likewise Brown/wood for common association.
Wall ... the missing wall should be rendered different ... like you have ... but could also be color.
Only trial and error will ultimately show what works with the colors.
Beyond the color, projecting light grey shadows could reveal a lot of details about the windows and roof shape.
It might be worth pursuing to use solid letters like you have for physical items, but label spaces like 'Nave' with an outline font to distinguish spaces from things.
Good luck finding someone with better color vision/sense than me to advise you on actual colors to try.
Last edited by atpollard; 10-22-2012 at 05:21 PM.