For paint-grade cabinet boxes, I usually recommend 3/4" birch plywood. It handles well and takes paint well. For door and drawer fronts, I recommend poplar for the stiles and rails. Poplar mills well and again, it takes primer and paint very well. For the door and drawer panels you could again use birch plywood; 1/4" to 1/2" thick depending on things. 1/4" is easier, but the doors may seem a little bit too light. Half-inch provides a more substantive feel when you operate the door, it can make a stronger and sturdier door too, but the added thickness of the panel can require a few extra cuts around the perimeter of the panel to get a nice recessed reveal for the front of the flat panel. On the flip side, the extra effort can give you a bit more detail on the inside of the panel when the door is open. But I'm getting ahead of myself. If you want nice quality shaker paint-grade cabinetry: Birch ply (3/4") for the cabinet carcasses, tops, sides, and bottoms. Half-inch birch ply for the cabinet backs. Poplar for the drawer and door stiles and rails. Half-inch birch ply for the door and drawer panels. If you decide to use 1/4" ply instead of 1/2" ply for the door and drawer panels, then you could use 1/4" for the cabinet backs too. By using the same thickness ply for both you can minimize waste when you make your cut lists. Poplar and birch ply are available at Home Sleepo, etc. I usually recommend staying away from MDF for kitchen and bath cabinet cabinets. If you do source the fronts yourself, yes, you can get them unfinished and then prime and paint them yourself.

"My teeny guest bathroom has a tub with shower, toilet and a sink with cabinet underneath."-that's exactly what I have in our new kids'/guest bathroom(just no floor to ceiling storage...we had a niche made between the studs though, and put there the longest recessed cabinet we could find, and painted it the color of the walls) And I also think "oh so tiny" But the truth it-it's the full bathroom..where all guests' needs can be accommodated. We had less when we were a family of six..:) And the sinks were mostly pedestal then..so no, I wouldn't change for the real pedestal, as nice as they look. Remembering all the pedestal sinks I had to use when young, and sometimes now as a guest, who hardly has a spot to put all her stuff on, and be in a hurry as to let other guests/hosting family use the bathroom too. You can go for airier, more open sink cabinet...that at least leaves you with shelves, and some sort of a counter..less time spent picking all that stuff you dropped when trying to apply your make up. If you ask me.. As for the color.. I believe in small space you can do everything to try and make it look bigger. But then you can throw this "bigger" to hell sometimes. You can go-and make it cozier. Small spaces are often cozy-why not to play along. Or you can decide to make it bold and interesting-so the actual size is forgotten, simply because there are other cool things to look at. Or you can wash it all in one color as beckysharp suggested-whether darker or lighter, it has a big chance to work because you notice boundaries less. (and that's what I did with mine. I was also limited by previous owners' tile choice..the tile was busy enough and lets say didn't justify use of wallpaper..the wallpaper that I eventually found that would look great with it, was big money. I decided my piggie of a bathroom will do without this lipstick...But laminate should be easier, in this regard, if you decide to pair it with pattern, whether very simple like stripes, or more complicated as florals-both work great with cottage look. Stripes make walls look longer too..) With a cottage/farmhouse look, I see whites, grays, blues, greens, yellows..I can easily see wallpaper as well, only this is more money/effort.. What color is your floor?

It looks like real tongue-in-groove paneling and not that cheapo stuff that comes in 4' X 8' sheets. You could paint it, although you may have to use either sandpaper, liquid sandpaper, or an appropriate primer first. It could have sheetrock under it, or it could simply be fastened to nailing strips attached to the wall studs. I would ultimately choose to remove it and have a clean, painted, sheetrock surface, but that would likely be a lot of work.

is the tile flooring same everywhere? does it stay? if yes-then in rooms you have it, I would go with not too stark, warm colors..smth like cream or tan or maybe driftwood..you know that very warm greige? and I would add cooler accents like blues and greens and whites etc in accessories you still can have this coastal vibe..sand and water.. you need to make sure all colors relate of course. in their temperature so to say. and clean starkness vs certain murky-ness..I hope I explain myself well, I'm not sure of it. or-another option-bold dark deep colors that are strong enough to be next to the tile.. i think quiet cooler pastels won't be great next to the tile..it's a type of tile that wins. needs either similar tone next to it-or something like that deep aubergine if the flooring is different in the other bath then it's a different story for that bath wood in vanities, from what i see, would work with almost everything, it's a very versatile stain I'd consider the flooring first of all, because it's the bossiest elements of them all.