I guess the question this brings up for me is what was your initial intention to establish boundaries in where the player could move. Were certain chunks "dead ends" where just nothing else would load? Or were there going to be chunks that clearly had barriers to moving further, aka trees/mountains/water/angry mob? I do think if it were the former, that could be very immersion breaking and I'd personally want to avoid that. However, the other option would necessitate "filler chunks" outside the barrier points, though I can't imagine you'd need more than one in any direction due to the camera angles. This does put it back into a similar realm as Mardek's camera and maps, but I'd say it would look very good. Alternatively, a "default" tile covered in a thick fog that extends slightly onto the boundary tiles might work and be easier than filler tiles, while being very clear that those areas are a no-go.