There's no rule that it has to be king size.
You can start with a small wall hanging sized quilt. Great practice, and you can work on your stitches and rhythm.
I'm personally very drawn to Welsh quilts. I find the patterns on them much more interesting (and contemporary) than traditional ones.
And there's no reason you can draw or doodle your own design.
I've seen some Zentangles that scream to be made in to whole cloth quilts. To me anyway. ;-)
Pippa has a great blog and a fabulous collection of Welsh quilts.
http://welshquilts.blogspot.com/
Also, there was a really good book that came out a few years ago on Welsh quilts.
http://www.amazon.com/Making-Welsh-Q...7983530&sr=8-1