penders - 12:02 am on Feb 19, 2012 (gmt 0)
I just did a quick test and both Chrome and IE (versions 6-9) correctly ignore this value.
Sorry, correction (again!)... "IE8+ correctly ignores this value. However, IE6-7 appear to treat 'yes-repeat' like 'repeat' and results in a repeating background!?" - although I still don't think this helps you much.
(I really should get more sleep!)