Wonderful! When I don't know what I'm talking about, Pati does. How great is that? Thank you, Pati. Polly
"Pati, in Phx" Not Polly, but this is something I was thinking needed to be discussed a bit. Kona Bay and Kona are different< very different. Kona Bay is a fairly tightly woven, smooth fabric and is wonderful to use for piecing and such. A lot of Kona Bay fabrics are Asian prints. Kona cotton is from the Robert Kaufman company. It is a "thicker" fabric, not as tightly woven and a bit less "sheer". Kona is great for embroidery, Kona Bay may be a bit tight and a bit too "thin" to work as well. Do cut your background pieces oversize and plan to trim to size just before you sew them together. Kona can ravel a bit, even just sitting.
Both Kona by Kaufman and Kona Bay are good fabrics, but they are best used for different things. I would use Kona cotton as an applique background, but not for any delicate applique pieces. Kona Bay is great to use for those tiny applique parts and such.
As for using Fusions or such, it depends on what effect you are going for. Personally, I like to use a much more subtle background for embroidery, and think that a solid (or a light "marble" or "hand dye" look) helps to set off the embroidery. Too much print in the background, even a tone on tone, can "fight" for attention with the embroidery. YMMV. Muslins do vary in quality. I used RocLon muslin for my Dear Jane quilt and it is great. But I also have gotten really cheap quality muslins that I wouldn't use for anything that I expected to last. And cost is not always the best way to determine quality.
Best suggestion is probably to get some samples of possible backgrounds and do a few test stitches, including a bit of traveling to see how it looks. Then get lots of whatever you decide to use.