What a fun room! Looking at modern quilts I would suggest nice colourful squares or rectangles sashed & bordered with white. You could add some prairie points in the border if you didn't want it plain. Here's a link to some really neat quilts to choose from.
https://www.google.ca/search?q=moder...w=1229&bih=859
This one really looks like fun!
http://www.ohfransson.com/oh_fransso...ilt-along.html