I would probably pull a softened cone up from under the ground plane as I had a stream of particles flow across its surface. To make the illusion work better I would put the camera in a position that we can't see inside the container that the sand is dumping from
Its pretty good, but off the top of my head I would say the spokes on the wheels and the wheel thickness suggest iron instead of wood. Also everything is all nice and uniform, your could select individual poles and tweak them 1/2 a degree in a random direction and it would look more hand made.
I bet the big slowdown is your choice of textures for the walls. It looks like one of the plug in textures. They all look cool but they slow the renderings to a crawl. Test it by making the walls plain gray and checking the results, I am betting less than an hour
Compress the hell out of that and it would show up on those youtube crash compilation videos. It looks good. very real.
One thing I found makes for better smoke is to use at least three emitters with significantly different size particles that add up to the same number of particles that you are using now.
The blue around the eye is the eye lid. look at the birds feet, see the lovely shade of blue. This birds skin is blue, lots of birds have blue skin. If you look real close at the eye on your photo you just make out the wrinkles in the birds eyelid.
With splines you don't need quite so many control points. I would say that you could get the same shape with maybe a quarter of the control points. If you are doing a face you may do a lot of CPs to give you more options for rigging but beaks are rigid and adding all of these CPs may slow things down one you have a whole bird attached to it. I am impressed that you were able to keep things so smooth with that many points.
You are making good progress, but down in the center of the chest it looks like you might have a couple of fishnet splines that will cause problems later on. Your control point intersections look like the splines are making right angles with themselves rather than being more or less continuous curved lines. If I have time this afternoon I will fire up photoshop and circle the splines in question. You want to fix this before you go to much farther, as it will cause problems with copy flip attach comands.
I a starting my steam punk Short. So using a Top down methodology I am starting with the control panel, working out to the wheel house then to the boiler and engine room, and then throwing a skin on the whole thing.
Here is the gauge panel. the colors are place holders at this point.
another thing you can do is to add a turbulence "nozzle". add a force near the the emitter in the same direction as the emitter with some turbulence in it, it should radomize things nicely.
one thing that can cause the bump I am seeing at the end of the loop, is where you have your last frame the same as the first frame. If this is the case ending the render one frame early fixes it.
I agree with vern about the wear patterns, but the one thing I noticed, is that the front sling holder is passing through some of the nurbing (cooling fins maybe?) that is something that you can fix during rigging, so I wouldn't stress about it.