I am a firm believer in oomph-y baseboards - I have come to detest skimpy baseboards (and other moldings), they just look cheap IMO unless it's a very modern house with minimalist moldings everywhere. Our current house has 6 1/2"-ish (just a 1x6" - which is really only 5 1/2" - with a 1" cap molding on top, cheap, simple, and snazzy looking) baseboards in the master suite but we never got to fixing the builder-blecch 3 1/2" "phony Colonial" ones in the rest of the house and I think they look so chintzy. Is the baseboard going to be painted? You should be able to rout a nice edge around the cutout for the AC vent, or use a bit of 1x1 stock (for example, I don't know what your vent cover looks like) to bump out the vent hole so that the front of the vent will be flush with the baseboard. Trim it out with a nice piece of molding that goes prettily with the top profile of the baseboard. If the baseboard's going to be painted, the toilet supply issue is easy-peasy! Just cut the baseboard in two sections, each with half the cutout for the toilet supply which I'm sure can be done with a hole saw that costs about 10 bucks at HD and goes on any electric drill. Fit them together around the supply, smooth out the seam with paintable caulk or wood filler, paint and tah-daaah! Put a nice cover plate, aka an escutcheon, around the pipe to cover the hole.

impossible to see. best guess would be fire rated foam, caulk doesn't dry & fall into bits, it falls in strips like it is applied. rather than try to dig it out, use Hardcast brand #1402 mastic tape & seal from inside housing of fan to sheetrock ceiling. this will keep particles from falling out, and provide an air seal at the opening cut into the sheetrock. keep the mastic tape within the area of the ceiling covered by the cover of the fan. you do know how to remove the cover of the fan? turn off light at light switch. take off cover for light bulb, remove light bulb, undo acorn screw. this will allow cover to drop. holding the cover in place will be the plug in for the light, which is a regular plug with the outlet inside of housing. unplug. the metal bulb housing is seperate from plastic cover. (this is the pic I was asking for...) hardcast mastic 1402 tape is available at hvac supply & is the best product I've found in 15+ years to seal metal to sheetrock (& many other surfaces) surfaces must be clean & dry. while I don't have a pic of a sealed housing for bath fan, it is the same process as for sealing supply boxes (for hvac) to ceilings. below is pic. best of luck. best of luck.

The dark grey tile will be on the walls of the shower/wet room and the curb. The pebbles will be on the floor of the shower. The white ish tile is on the main bathroom floor. The vanity backsplash and wall will be clear glass tile and the inside of the shower niches will also be a smaller clear glass tile. The vanity will be a teak floating vanity. The bathroom will have teak accents (shower bench, tub tray, etc). The door is painted white and is a 2 panel shaker door. The baseboards throughout the house are simple flat front 6" tall and painted white. I know that’s more info than you need but will hopefully paint an image of the style.

Whats standard? Might depend on where you live. :-) In Arizona, my tract builder routinely used grout to seal the gap between the tile and the baseboard (they used *nothing* between the carpet and baseboard). I never had any complaints with the grout, even after our house flooded. In Texas, my tract builder routinely used caulk to seal the gap between the tile and the baseboard (again, nothing was used between carpet and baseboard). I, personally, dislike the aesthetics of white caulk (to match white baseboards) running along the bottom of every wall -- it has always reminded me of a bathroom. When I viewed the model homes, it felt like I was walking through a ginormous bathroom. :-/ As an experiment, my husband beautifully installed beadboard and beefy baseboards in our pantry, and when he sealed the baseboard/floor, he used a very thin line of caulk that matched the *grout*. It looks a million times better. I remember asking a similar question here on GardenWeb, a few years back, when my current home was being built... And I think it was a member named "worthy" who mentioned using caulk as a barrier for insects. That pretty much sold me on the idea, since we have fire ants here (had over 300 scorpions in our house in AZ, the first year we lived there; I'll take fire ants any time!). Unfortunately, you'd have to caulk/grout EVERY baseboard, which tract builders won't typically do if you have carpet anywhere. Based on your photos (except the first one -- that's really sloppy), I love that the builder seems to have tiled *to the wall* and then put the baseboards on. My builder -- sigh -- tiled roughly 1/4 of an inch away from where they anticipated the baseboard would be (I actually have 1/2" of caulked space between tile and baseboard in a hallway), so I have a ton of horizontal caulk lines all over the place that trap dirt and shrink up. Scrubbing caulk with baby wipes is fun. :-/