I'm having the same problem here. I think if you extend
"AccordionHeader" and make a component in action script for each
button, setting the "headerStyleName" to an image or using code to
style it, you can put them in the accordion. Where and how I
haven't figured out yet, but that's my first suggestion.
Otherwise, I'd try to extend "headerRenderer" and use
getHeaderAt( //index ) somehow. I think this is the way to go, but
I haven't figured out exactly how just yet.
I want to try "getHeaderAt( //index ).setStyle( "fillColors",
["#uint , #uint"] );"
I think this kinda works, you still can't put an image as the
background or have rounded corners at the top and normal corners at
the bottom. That's the hard part, putting rounded corners at the
top and right angle corners at the bottom.