DaveHawk, I think I understand the artistic delema you're grappling with. I used to draw fairly well but gave that up in favor of learning to play drums, guitar and bass (in that order). I'm far from being a prodigy when either writing or playing music, but I'm accomplished enough to know when not to "overplay." There's a great feeling of power and awe when I'm able to burn through a minor or major 5th scale so fast and accurately that I crack myself up. But when I listen to the playback I think; "Know what? I'm overplaying. So what if I can burn off a bunch of notes -it doesn't fit."
Got an idea: do a quick 2nd sketch and draw the creek in. If you don't like what you see, don't add the stream to the final rendering. You'll know if it "fits" or not.
I really can't tell you whether or not you should add the mountain spring or not. What I'm trying to say in my longwinded way is: only (play or) paint what fits. I'm comparing music with your art; they're somewhat comparable. I can't stand bass players who solo over the vocal portion of a song -it's almost as bad having no rythum, no sence of melody or playing nothing but flat 7ths all over the place because someone thinks they sound bitchin'. There's a subtle art and stately beauty to simplicity that no amount of flash can replace. But if the song (OR the subject matter) lends itself to shredding thousands of 32th notes into a single 12 bar passage, I say go ahead and burn yourself down. If the scene or subject matter you're creating screams out for more detail, movement or action add flushing quail, a waterfall or whatever. The thing is; does it fit?
Again, there's a dramatic statement to be made by keeping things simple. Your elk picture nearly takes my breath away because it looks so real. If you add anything, be sure it doesn't dilute what you've got nearly perfect so far. DD