The only Rivellon maps are the in-game ones, at least so far. The Lore book being written for D:OS 2 may get into the geography and its evolution.
There were a couple map areas dropped from Divinity 2. I'd guess some attention was paid to the previous map, but 'magic' was an easy excuse to do things differently (especially since non-flat landscapes needed to be introduced), in addition to natural changes (swamp encroaching on the farmlands in Beyond Divinity).
