or any other bubble accent tile suggestion? this one is like $30/sf :(

I think a polished ceramic subway tile will work really well with this. You can go for bigger subways such as 4x10 to make it more modern.

I'd stay away from any warm tone tiles with this border.

This looks like a perfect accent for a fun kid's bath, without being so juvenile that it will look childish as the kids grow up. I agree that a polished white tile (subway or squares) would be the way to go, both aesthetically and economically. If you want to add a little color a pale blue or green might complement it well - I would definitely get a sample of that tile and grout it before chosing a color other than white though.

HD has some bubble tiles at about 1/2 the price: "Merola Tile Cosmo Bubble White 11-1/4 in. x 12 in. Porcelain Wall Tile is a porcelain mosaic that features circular tile chips in different sizes and finishes for a varied look. Matte, glossy and iridescent glazes make this tile stand out"

We used Porcelanosa's White Thassos marble circle/bubble mosaic in our MB. For field tile, we used large format 12x24 glossy white tile, also from Porcelanosa (I have to look up which exact one).

cat mom, which vanity do you have there? It looks just like what I was looking for.

The sinktop is from Sonia. The vanity is modeled after the Sonia Europa (?). We had all three of our vanities built by a local guy. He made them a little taller than the Sonia's (ours are 36" with the tops, Sonia vanities were only 31" tall give or take) which allowed for taller open space behind the doors, and taller drawers. Much more comfortable to use at the taller height, too.