Basted Hexagons

I have made great progress in the "concentric hexagons" quilt project I started a while ago using the pre-cut fabric kindly gifted to me. I had made up all the half hexagons at my retreat back in November, and I took them with me to Perth at Christmas to work on the final layout of the quilt. While I was there I stitched together the half-hexagons into rows, and at the MMQG SASD I stitched the rows together and the borders around the outside... except when I got home I realised that I had put the borders on the wrong edges, and rather than making the quilt square had succeeded in making it more rectangular! oops! I spent some time this evening unpicking the borders and re-sewing them back onto the correct sides, and thus finally finishing the quilt top:

I had decided for this project to challenge myself to try and make something with a modern aesthetic despite using the very traditional styled fabrics. The key to my "vision" was negative space, which was filled perfectly by some homespun from spotlight in pretty much exactly the same colour as the solid cream in the range.

What do you think? Am I on course for making a "modern" quilt from the "traditional" fabrics? 

One of the fat quarters had the name of the range on the selvage, which meant that I could look it up and managed to buy some on the internet from Lonestar Quilting for the backing and borders. The range is Wiscasset by Moda, and I chose this large "cheater quilts" print for the backing, because I quite like the print and it was completely lost having been cut up for the hexagons. I particularly like how it's got several of the prints from the line within its design.

After finishing the quilt top, the rest of my evening was spent basting the quilt (in the sanctuary of my air conditioned living room). I intend to machine quilt this one, so I had intended to spray baste it, but forgot to buy more spray. Since I had the evening free, rather than wait until I have some spray I decided to pin baste it instead. Hopefully the pins won't be too much of a pain when it comes to the machine quilting (I'm planning to free motion quilt it), I've only used pin basting for hand quilting so far.

Lastly, I'd please like some opinions on what colour bobbin thread to use when quilting. I have some cream that matches the solid for the top, and was probably thinking Navy for the bobbin (ie back). The tension when quilting is pretty good on my machine, so it's unlikely to show through to the front but it's possible.... What would you use?