I wonder how your dreams are the same as mines
Animated tiles: that's always been one the first things I added to my old rpgs. I'm always pushing for them since I think they could add a lot with little effort.
Birds/bugs: they could already be added by means of overlay images and particles, at least I know of Pajarico attempting to add birds by overlay and Crush adding bees by particles. They're still limited since as far as I know the overlay effect doesn't support random movements (Crush, correct me if I'm wrong)
Location based sounds: yep that's already been discussed. With the current SDL_Mixer support and object groups on maps it should definitely be possible, it is just a matter of time in my opinion.
Epic sized monsters: again that should already be possible, since the graphic engine should render them correctly, what would be weird is that their area will still be one tile. IIRC you made one big boss we could test with.