From my research, the key to getting a Byzantine look is the shallow dome, with the slightly flared lip, and the church-like aisles with a central nave. The semicircular apses at the front and back, and occasionally overlapping roof elements also help.
If your good at landscape painting, use that to your advantage. You can incorporate those elements into your maps (that is kinda what I meant when I said abstract -- a map doesn't have to look like maps you've seen elsewhere; make the map in your own style, and play to your strengths while your at it). The best maps I've seen (and tried to emulate) are ones where the central mappy section is complimented with nearby doodles, sketches, building plans, notes, etc. It makes it look like the cartographer is not only trying to show a place, but give the viewer some of the flavour of that place, too. And as far as I know, there's no reason that shouldn't be appropriate for a novel.