So, after some suggestions and some thinking, I decided that a recessed gutter would look better than a raised curb for this table. It would also be more practical as the curb could interfere with some terrain placement.
Additionally, I replaced several areas of blocks with some foamcore I had laying around. I am planning to cover some large swathes of the cobblestone in snow drifts, so there is no reason to cover up the completely good tiles I worked so hard to cast. This has the added bonus of leaving me more leftover tiles to make some board expansions in the indefinite future.
Any other suggestions? I think I will start gluing down the tiles this week, time (and glue permitting)!