I think you can ignore "bildhaft", as it's obvious from the context that they're pictures.

Working with parts of a building in an abstract visual way in an architectural context calls for the word "frames" (even though that's not the question). My suggestion is "abstract visual frames". See if it feels good in your context.

or perhaps even "vivid schematics"

"Focusing on important projects of the architecture firm, the current exhibition showcases its full range of expertise by presenting sectional schematic views/images of the building facades."

I am not sure there's a definition available in current German that implies that you can abstract something out of something else without obtaining a result that's more abstract than the source. Just by rendering a particular set of features in isolation and out of context, it becomes more abstract, no..?

The German sentence could use some work, too. It would read better like this:

"Die aktuelle Ausstellung portraitiert wichtige Projekte des Architekturbüros in ihrer gesamten Bandbreite anhand von bildhaft abstrahierter Ausschnitte der Gebäudehüllen."