I changed from a 24" vanity to a 26" pedestal. (To be honest, I measured so long prior to ordering, I didn't realize I was ordering a larger sink. Oops.) You want to make certain you meet code with the distance between the sink and the toilet. I believe 30" is the building code (though someone with actual professional experience is welcome to correct me). Other than that, you should take into consideration the location of your plumbing (and whether you can move it), how close to the wall you want your sink, and whether your walls are square. I ended up moving my plumbing slightly in order to meet the specifications of my pedestal sink. Because a pedestal sink exposes more of the wall underneath, having the plumbing neatly tucked behind the pedestal (as much as possible) is nice. I also chose to have a mostly 1" gap between the wall and the sink because the wall is not square. This was a powder room (can't recall the dimensions off hand) and I used 16x16 set on the square. In my opinion, larger tiles (12x12+) can add a feeling of spaciousness. But, I also like small mosaic-style tiles. It's really just a personal preference. You could look for inspiration pictures (such as on sites like Houzz.com) to see different sizes of tiles and how they visually impact the appearance of the room.

Are you having the glass top cut to order? If so I would think that would be the person to get the best information.

My first floor powder room is 4' x 5' 8" so almost the same size as yours.The sink is 25" across The lower level powder room is only 4' x 5' but the sink is 27 " wide. As you can see it looks a little crowded in there ( please disregard the missing baseboard trim) but it would probably look fine in a room that was 6 inches wider like yours will be

Nothing is standard. You aren’t saving $100 to try to hack a kludge either. Do it right or don’t do it.