I understand the frustration! Ordering swatches for everything you intend isn't the most economical thing, but things do vary a lot by fabric type and it seems like the most reliable way to know what you'll be getting. My samples look plenty black, the file is set up to be pure black, but every fabric picks it up differently and every lighting and flash from a camera seem to make it look different..
Here's some things folk's have made that might help a little...
I wish the options carefully (as possible) stated the background color. I wish the fabric selection stated the thread content more carefully, eg 100% polyester, etc.
I made one garment from this fabric designand am now making another because of the above comments. I'm just not satisfied with the finished product, so back to the drawing board!
If you have questions about that, you should ask Spoonflower's customer service directly: http://help.spoonflower.com/ I am only a designer creating art, I don't print and ship the fabrics myself. I will note that my experience is that the whole order places will ship together. I've never had anything sent separately.