Photos are needed to really help you. I can tell you that a standard vanity size for your space would be 48". You would then use a filler for the additional 1.5" if you were to chose a standard wall to wall vanity configuration. I think based on what you have told us a wall mounted or stand alone vanity would fit in with your style. If you go that route, you would need to go smaller than 48". Post some photos please.

This is the space. That light fixture will be coming down as well with something updated to be put in its place. Thanks for any suggestions.

If you go smaller, you'll need to consider cleaning the floor along the sides. An open bottom where you can dust and mop under it will help. Drawers are one of the things that drives up prices and you don't need many of those for a guest bath.

We gutted our hall bath and replaced a built-in 48" vanity with a free standing 36" vanity. Plumber thought we were crazy-LOL! But, given the very narrow entryway, I wondered how we could have maneuvered a 48" vanity into the space... We actually removed two vanities, but replaced only one. The plumber capped off the water line on the abandoned side, and DD now has a custom work surface in that alcove for her morning hair & makeup routine. Here is the sink alcove:

That is almost exactly how ours would look and I love it! I even like it without the tile backsplash...My mirror fills the space although it is framed differently than yours. I think we will proceed with this plan. If you have a picture that shows it from the front that would be much appreciated. Thank you so much!

Why would you want to leave the small gaps?!

You can go to any Kitchen/ bath place and customize a shaker style or any style to fill the space, add a top, have back and side splashes!

No point at all to small "gaposis , when the look in the phot is easily replicated to FILL the niche

Trust me, you want a wall to wall counter, absolutely, no doubt about it, I kid thee not.

Buying a vanity that comes with a top will be much cheaper than having a counter fabricated. Go price it all out and make your own decisions.

pbooth1197 - Here are some pics.

Given space constraints in the hallway and entry to bathroom, we didn't want to deal with a 48" vanity, and I didn't want to cobble together small base units. I liked the idea of a custom floating vanity like this one, but DH was only beginning his foray into carpentry, and didn't want to take it on.

The original vanities were locally-built and set in place before the finish plumbing. The mirror is original (1994). We framed it and added the beadboard wainscoting in both alcoves. Note: DD was 12 at the time, and picked out the tile, grout, paint, and vanity (we also replaced a tub-shower insert with a new tub & tiled surround).

Originally DD picked out a vanity on Wayfair, but they sent it to Charleston just before hurricane Matthew, and the freight company was too frazzled to get it on the Savannah truck. We were all using one bathroom, and nobody was happy. After several instances where they called to reschedule delivery, then didn't deliver, I got on the phone to Wayfair, got my refund, and DD picked out this one at Lowes:

And the gap:

Yes, her stuff drops into the gap. Yes, cat toys get under the vanity. So what; we like it. I love "built-in" (we kept the original vanity in our MB, and added vessel sinks), but sometimes freestanding is better. The scale is good for the space and we are all happy with how the room turned out.

It's very nice. Is the top drawer a partial because of the sink? Who makes that vanity?

mayflowers Yes, it's a partial drawer. We usually keep washcloths in there

mayflowersMIx & match vanity and top from Lowes. The Moen faucet was purchased at a local plumbing supplier. We didn't use the marble backsplash, due to the mirror. I still have it; open to ideas on how to re-purpose it :)