How about a Renaissance/Camelot inspired room? Get posters/artwork that shows castles, kings, queens, etc:
http://homedecorators30.artselect.com/perl/search?sortType=MostRelevant&t=c8436&openct10171=10169,8436&alt=Castles-Knights
Tapestries:
http://www.homedecorators.com/Home_Decor/Home_Accents/Tapestries/
Bedding with brocade designs - what you would imagine to see in a mediavel castle:
http://www.overstock.com/Home-Garden/Monte-Carlo-Jacquard-Comforter-Set/1037026/product.html?
http://www.overstock.com/Home-Garden/Asheboro-Luxury-9-piece-Comforter-Set/3063185/product.html?
http://www.overstock.com/Home-Garden/Royal-Paisley-24-piece-Luxury-Bed-Ensemble/3141170/product.html?
http://www.overstock.com/Home-Garden/Corsica-8-piece-Bedding-Ensemble/3024623/product.html?
Since you mention you like waterfalls, then maybe get one:
http://www.homedecorators.com/Home_Decor/Home_Accents/Indoor_Fountains/
A wallpaper that looks like stone would complete the look:
http://www.americanblinds.com/products/wallpaper/product_detail.asp?ptn=WW207&prid=974054&sterm=keyword&Nrpp=60&P=WP&results=1&Ntt=stone&N=4294967258&sval=stone&Nty=1&cm_re=A%2D%5F%2DTop+Nav%2D%5F%2DWallpaper&Ntx=mode+matchallpartial&si=5&No=120&Ntk=search%5Fpattern
http://www.americanblinds.com/products/wallpaper/product_detail.asp?ptn=WW210&prid=974060&sterm=keyword&Nrpp=60&P=WP&results=1&Ntt=stone&N=4294967258&sval=stone&Nty=1&cm_re=A%2D%5F%2DTop+Nav%2D%5F%2DWallpaper&Ntx=mode+matchallpartial&si=5&No=120&Ntk=search%5Fpattern
But a floral would look quite nice, too:
http://www.americanblinds.com/products/wallpaper/product_detail.asp?ptn=5511934&prid=1053175&sterm=keyword&Nrpp=60&P=WP&results=1&Ntt=stone&N=4294967258&sval=stone&Nty=1&cm_re=A%2D%5F%2DTop+Nav%2D%5F%2DWallpaper&Ntx=mode+matchallpartial&si=5&No=0&Ntk=search%5Fpattern