Those large ZipLoc bags mentioned above are great - they won't ever get mistaken for garbage.
I usually find them at Target
http://www.target.com/p/ziploc-big-bags-xl-4-ct/-/A-12971772
They're around $6 for 2 or 3 depending on the size.
The is also an XXL3 that's a bit smaller then the one in the link.
And congratulations on having your quilt juried in.
Good luck!