If I may, and only if this is the type of site that’s going to grow large over a long period, I would take bep’s recommendation a step further and remove all path-related info from the content so that the image is related strictly to the content itself and not any specific URL pattern or site architecture. I don’t know how you’re organizing the images overall, but you can use page variables like .Section, or .URL in conjunction with what you’re already doing…
It has the added benefit of less typing in the front matter (i.e. and therefore less room for human error), which speaks well to my laziness tendencies.