For a future update, I would love the option to tile or not to tile an image in a Texture Background.
It’s really frustrating to have to try dozens of image sizes until you get it to the size where it won’t tile and fills the screen. It would be sooooooooooooooo much nicer to have a lovely little tick box that says Fill Screen!
It’s a tiny thing but, I’d like it! 
Here’s a possible workaround :
Remove the texture background from Preferences. Then go to Project->Project Settings…->Background Images. Set the Composition Mode background to what you will.
You will need to do this for every project,
Hope this helps!
OMG Silverdragon, that works like a charm!
I wish I’d known that option was there before. Not only do I fight on getting it to stop tiling, I change the background every time I open the particular book I’m working on (as I write more than one at a time).
You’ve saved me so much time, thank you!