First off, I'd like to share my process for scratch building an oasis terrain piece. With slight modification, I am sure this would work for any sort of pond or pool.
First I got a round wooden disk six or eight inches in diameter. This was maybe $1.20 at the craft store but I'll bet you could improvise a simple, stiff circle from any number of household objects. Onto it, I glued the water. I am aware that there are special paints and gels to create a rippling, translucent water effect, but I came up with something simple, economical, and convincing: I got some shiny blue tissue paper (the sort you'd stuff in a gift bag or use as wrapping paper -- super cheap at the craft store) and crumpled it up. This crinkled effect catches the ambient light in a way that is reminiscent of water rippling under a breeze. Next you'll want to glue on some trees; I had some palms that were undoubtedly intended to go into a fish tank. I converted some Christmas pine tree and holly berry clusters (part of a dollar store holiday corsage) to pomegranate trees just by painting the cones green. I didn't glue trees in an even circle around the spring because nature is often asymmetrical, and because I thought there might come a day when figures would want to stand on the piece. Next you glue sand around the tissue paper. Use the glue and sand to cover the ragged edges of your tissue paper -- it does not cut cleanly -- and to hold and hide the point where your trees meet the wood. When it's dry, paint the sand with a wet brown. When that is dry, drybrush the topmost surface of the sand with a yellowish tan. Trust me -- you want to paint your sand this way. Sand painted to look like sand looks much better than sand. I know how ridiculous that sounds. Glue a little greenery around the water and there you have it. Here's the oasis under a couple of lighting conditions.
I did not actually look up any pictures of oases while creating this, preferring to build an oasis of the mind, lit by the lamp of the mind.
When will this oasis see action? There has been some loose talk of a Defend the Oasis scenario (based on a scenario from the Hail Caesar book) pitting my Persians against GG's Romans (ahistorical: Persians did fight Romans, but my Persians come from the time of the Greco-Persian wars). GG's Romans put a stout whooping on us last time, so I have hurled myself into painting some Persian forces.
These guys aren't really Persians, they're Indian levies. These are Eureka miniatures and I'm fond of the sculpts. In the rules these guys are not very tough, but that's no reason they shouldn't look good. I really like the palette of warm earth tones on these guys. And yes, that is purple on the shadowy parts of the levies' skin. It isn't realistic but it's very pleasing to my eye. The only thing I'm not sure I like here is the lack of eyeballs. I've been leaning against painting eyeballs on soldiers recently but maybe these guys need them. Do you put eyeballs on your minis?
Persian heavy cavalry. These guys actually have a strategic use: they'll be the one unit in my army that can dish out more head-to-head clash damage than a Roman legion. I would devastate a legion if I hit it in the flank, and, if Ahura Mazda is on my side, I could even punch a hole through his center, if I am properly supported. Positive points: I love painting scale mail. Negatives: these guys just aren't that terrifying. They're Old Glory miniatures. The picture on their website was hazy enough that I couldn't see that they were all holding bunches of javelins. None of them are even holding them in an active "I'm going to javelin your ass" pose. I would have preferred swords, spears, and axes (heavy cavalry are most useful as shock troops) held in attacking postures.