The idea letting the river move to the left side of the aquascape is certainly interesting (though would be difficult to change). I see many things that doing that would strengthen. However, my main concern with rivers/water features in layouts is that they often come accross as an after-thought. My intention was to not allow this to happoen, as scapes with streams too close to the edge of the aquarium always seem unbalanced to me. The sand is the brightest part of the aquascape, and moving it to a location that's off to the side (not in line with focal points) can cause problems when it comes to the viewer's eyes. However, I'm sure it could be done well-- I just haven't seen an example of it yet. There's a limit to how many risks/experiments I want to do in the same layout.
Some of my aquasketches are purely the result of drawing using a Wacom tablet, and then running the finished drawing through the Photoshop water-color filter. Usually, I like to use photos to make "pallets" in photoshop-- ie, by making a pallet by sucking up all the colors from a photo, it's possible to have a better idea of what colors one should use. This is especially useful when drawing wood! You probably don't know this, but wood is not just brown, it's also purple, green, blue, orange, yellow, gray and pink depending what part of it you're looking at!
This sketch is even more manipulation, and less drawing. I wasn't feeling particularly hard-working when I did this one, so instead of drawing (in the normal sense) I used a function of photoshop to design paint-brushes that are the same shape as the plants (I made 6 different "moss" brushes, a R. Najenshan brush, and the computer already has brushes designed for grass), then use the Clone Stamp with some photos to draw in the plants. This works really well, but still takes a lot of work and a sensitive hand. Especially when drawing the stem plants, one should pay close attention to how much pressure one is applying to the drawing pad. Rocks and wood still have to be drawn by hand, and there's no helping it. Clone stamp doesn't work for those either because of lighting conditions, desired texture locations, and other factors probably will be very different from any photo you'll find. Hand-drawing hardscape works really well anyway so I prefer to do that.
Also, care should be given when designing the brushes. It takes some drawing skill and attention to detail but the finished effect is nice. Larger-leaved plants or plants with "crowns" are not as easy to use this with-- anubias is pretty impossible. Hmmm . . . maybe I should do a tutorial on this? But then again, a method that requires expensive software (Photoshop CS), expensive hardware (my INTUOS pad runs over $200), and over 3 hours of time (this sketch took me 3 hours even with short cuts, some I've done were 10+) probably would not be popular for most people . . .