Don't go for plain curtains in a blue. You are trying to mix these denim tones with the brown without a bridge. You need to layer prints in to make these work together well. Here are some fabrics that would work in this room - this would make a great bench or ottoman - possibly a graphic pillow cover - http://beautifulfabric.com/asccustompages/products.asp?fav=0&fpage=1&page=1&categoryID=18&productID=5970&pStart=200&recNum=294
or more traditional pillow options http://beautifulfabric.com/asccustompages/products.asp?fav=0&fpage=1&page=1&categoryID=18&productID=8778&pStart=0&recNum=95
http://beautifulfabric.com/asccustompages/products.asp?fav=0&fpage=1&page=1&categoryID=18&productID=7242&pStart=200&recNum=304
this is the kind of curtain you might attempt - something plain in the gold undertones along the cream to camel range - pick up on the warmer tones in these prints (butter, soft dijon) that work well with both the chocolate and navy. like these sale panels in a camel menswear tone http://www.jcpenney.com/for-the-home/clearance/view-all/linden-street%25e2%2584%25a2-bartlett-grommet-top-curtain-panel/prod.jump?ppId=pp5001520231&catId=cat100260226&deptId=dept20022800026&Nao=48&pN=3&topDim=Color&topDimvalue=browns&dimCombo=Color%7C&dimComboVal=browns%7C&currentDim=Color&currentDimVal=browns&colorizedImg=DP0928201218510396C.tif&urlState=/window/shop-/curtains-drapes/browns/_/N-1noxaaZ133/cat.jump
At least flip pillows back to their own - recover them with a print.

You can go up into cream and camel from the chocolate, and up to sky in the blues. Don't mix in blue-greens - they are more often shown with brown but they won't work - stick with straight blue tones until you have enough to add a pop of a more blue-green shade in art or something with many blues. Consider this as a color inspiration for the room - follow the palette in it to get the result you want http://beautifulfabric.com/asccustompages/products.asp?fav=0&fpage=1&page=1&categoryID=21&productID=8916&pStart=0&recNum=173