When doing destruction, look at the material and break it accordingly. Wood planks wouldn't break into triangular chunks, and nor would brick walls. Breaking them up into individual bricks or planks would make it look a lot better unless there's some kind of funky magical forces causing them to break that way on purpose.
The wall in the inn seems weird too because it's just breaking into weirdly long planks and opening outwards almost. As for the floating island itself, it'd improve it a lot if you used displacements instead of just making it a big cone, then you could shape it more interestingly, and maybe add more flying debris and chunks of land floating elsewhere.
The skybox also seems pretty odd, If you've got your light_environment inside the actual map, then it won't light the 3d skybox, if you have your light_environment in the 3d skybox, it'll still work the same as it would if it was placed inside the map area. A custom skybox texture probably would've helped you out here, too, since most HL2 skyboxes don't have a bottom to them.
More detail like piles of debris and rubble around the buildings would look good, and maybe just some town props scattered around, it's weird how nowhere has windows, and the doorframes are all empty.
When making medieval maps as well, it's a good idea to look at reference material, since currently, to be fair, your buildings are just blocks with stone textures slapped on them, and aren't really very interesting
. If you have your own architectural style to fit the setting, that's fine, but it's a little bland if the buildings are meant to be blocky and simplistic. Detail in buildings always makes them look more interesting and beleivable. I know medieval architecture is hard to do and i'm not amazing at it myself, but it's easy to kind of recreate if you look at reference pictures and try to recreate styles.