I don't have a photo, but I used an old dry sink as the vanity in the little house. It was easy enough to cut a hole in the wooden top and drop in a porcelain sink :)

I did this in two of my bathrooms and love them both! The guest bathroom has an old sideboard as the sink. It has two storage cabinets on the side and will have two drawer boxes installed, which is plenty of storage for a guest bathroom. The bottom drawer was modified to flip up for easy access to plumbing. The master bathroom uses an old desk for the vanity. That plumbing is coming up through the floor so all of the drawers are still usable. The sideboard is taller so it's comfortable for a larger height range. Since the desk was made to be used from a seated position, it's shorter but so am I and I'm the main one that would use it. I would say the three biggest things to consider when thinking about using furniture for a sink is where the plumbing will run, the height and depth of the piece (make sure it has room for the basin and faucet) and how to protect it from moisture.

This will be the vanity in our main bathroom. We have one other half bath. It is just the two of us here, hubby and me. I have multiple disabilities and could be using a sit-down walker or a wheelchair any time. The knee hole in the vanity means I can roll up and use the sink in the center of this vanity easily. The other reason I chose this one is that I needed an 18" deep vanity due to widening the room door to 36" for accessibility. The tub will be replaced with a roll-in shower.

which is probably going to be the top of this pedestal sink. Talking about heights, the vanity is currently 31.5", but I need it much higher because my back is so stiff in the morning that I cannot bend. So this sink will add at least 3 - 4 inches, and maybe we will figure out how to add a stone counter top underneath it, adding another 1.5"! That is more like what I need!

The medicine cabinet is from Restoration Hardware, already taking up space in our third bedroom.

Those are not the tube sconces I have. The ones I have are from Pottery Barn and there will be one on either side of the cab above the vanity.

The second mirrored cab will be lower, and will have this light above it

The center drawer in the vanity will be lost, of course, but it will do a great job of hiding the deep sink basin, with the help of the apron under the drawer front. This sink is just a smidgen wider than the vanity is between the two fluted posts that delineate the drawer banks. The sink basin will easily fit in the drawer space. It is 17" wide and the drawer space is 20". It is not really obvious in the sink photo, but it also bows out in the front, as does the vanity.

I am not sure what color the vanity will be. It is mahogany under the milk paint, I was told. It has the rub-through effect with some cream paint and the mahogany showing through the corners and edges of the vanity. I may paint it to have an even color, or may also have rub-through. It could end up a blue, or violet. Right now, it is turquoise.