The idea for the small pond with water lilies comes from a very useful book from Model Railroader magazine called "The New Scenery Tips and Techniques". It's still available and very good value for anybody interested in scenery techniques:
http://www.kalmbachstore.com/12243.htmlIn there is an article by Gerry Leone about "Lily pads, cattails and pond scum" showing his methods of modelling a nice pond diorama. You can find this here
http://home.earthlink.net/~grleone/diorama.htm including some nice pics,

but unfortunately the link to the full article seems to not work any longer. So, basically it goes as follows:
Lily pads feature slightly concave borders; to get this effect, I cut two different sized pieces from brass tubing (about 6 and 4 mm diameters) and used my hobby drill with a grinding tool to sharpen one end of the tubes. Take a small piece of heavier paper and push around 4 to 5 blobs of different acrylic greens/olives/greenbrowns with a moist brush until the paper is covered, but don't try to mix the tones fully. Let dry. Then, on a soft material like a cutting mat, punch out the pads
from the uncoloured backside of the paper! Punch 6 to 10 pieces in one go from different color areas, then poke them out with a wooden dowel from the other end of the tube. Voila, concave borders! Now just slice out a triangular section with your sharp knife and the lily pads are ready to go to your pond.
Sounds easy? It is easy!