I am not sure it's possible to find a busier mosaic than the one you've chosen. It has different sizes, colors, shapes, and materials, both stone and glass, in a single sheet. If you were pairing it with the Quartz alone it might be ok. I think it is a bit of a mess pairing it up with your busy island stone. Do you really love that tile?

You don't have to go monochromatic with the tile, but I probably would, and I'd recommend a glazed ceramic tile or a glazed thin brick from Fireclay tile, over a stone or mosaic tile.

This is Fireclay thin brick in Silk.

If you have your heart set on glass tile, I'd go for a mosaic with an interesting shape in a single color. This is Pacific Tile's Wood ash cream beige arabesque.

But if your eye clamors for more color, more of a piece-y patchy look, you should try to choose a mosaic made of a single material in pieces of similar size and shape, that incorporates two or three complimentary shades of a single color, no more than that. Below is Botanical Glass in Cream Beige and Brown Beige sandwiched between your other materials. I hope you can see that while busier than the monochromatic choices, this mosaic is a more harmonious choice than the one you have above, because the busiest piece in the room is no longer the tile, it's the island stone.

If you have your heart set on a mosaic, try to find something that pleases your eye, but is a little simpler than the one you have now. Whatever you choose, your main focus should remain the island stone. Good luck!

The word that comes to mind when I see your color palette is "somber". Linen is the culprit. I've had many quartz samples at home for my projects (bought Caesarstone Buttermilk for my cherry kitchen) and I find those contemporary colors very difficult to design around. Photos of Linen installed make it look taupe, as I see some pink or purple undertones. I think these colors work best in contemporary homes with quiet, monochromatic color palettes, along with white or very dark cabinets. Maybe you're noticing the brown speckles up close and think this is what relates it to the granite and cherry.

I understand that you're shooting for transitional, but I don't think pairing a contemporary counter and stone mosaic BS (which some now call dated) with a traditional granite and cabinets is going to get you there. The type of granite, rich red cherry stain, and stone mosaic you've selected have been used in countless Tuscan style kitchens for well over a decade.