I've been concerned about the shadow clipping for a while now, and I've managed to keep most buildings low enough that it's either not a factor or hardly noticeable. I can let the shadow spill over, but I had some concerns (not knowing some of the inner workings of the game engine).
I assume the tiles are drawn first, then the buildings over the top? If that's the case, then most of the technical issues are not a factor. That leaves my last concern, which is that shadows spilling over to neighboring tiles won't properly fall on any of the neighboring structures. I.e. in the case below, if the park dropped a shadow on the tube to the university, it will appear "flat" across the tube.
On the plus side, in this very specific example of the park, the building is big enough that it obscures it's own shadow for the top left tube. So ultimately not a factor here, but it is a factor in some other cases (such as the attached comm tower). I originally had a smaller version of the park, but I felt that if people were going to go through the trouble of building a relatively non-utilitarian structure during a survival situation, it would probably be really over the top. I figure it's about the only place they have that calls back to natural instincts, so it would likely be a rather grand structure.
I think, for the most part, I can let the shadow spill over and work around the issues:
1) Very large buildings are also likely to be big enough to obscure their own shadow.
2) Any building that doesn't obscure it's own shadow (but tall enough to cast into a neighboring tile) is also likely narrow enough that the shadow falls into unoccupied areas of neighboring tiles.
3) Any other building not fitting into #1 or #2 can probably be adjusted to keep the shadow within the game tile (as has mostly been the case thus far).
Secondarily (if that's a real word), I am starting to get on board with increased color vibrance. I've intentionally kept many of the colors somewhat dark due to the atmosphere of the game (end of human civilization and all) and have stuck with the pallet that was worked out some months ago. Just like above, I do have some concerns. The tiles are so tight and everything packed in, I also want to avoid a situation where a large colony just starts to look like a lot of noise. Where there's so many buildings and they're all so loud/colorful that it's just a big canvas of abstract art. I'm not saying you did that with the park, but I'm mostly looking at the medical center (it's quite bright). I do like the feel of the park a bit more. It's lit up but not spectacularly bright. To me it makes it feel bigger.
Anyway, that's a lot of rambling. I'm not sure if it made any sense or went anywhere, but I guess I can say that I've been thinking about these things too.