Thanks for the heads up on that.
Does anyone have any general advice on how to practice animation from the ground up?

For example:  Things that you started out doing wrong that you wish you had known not to do from the get go and the opposite techniques you wish you would have started using from the beginning.

i knew what it was as soon as i saw this ;-)

I am pleased that you recognized it so quickly.  It means I didn't do too terribly at least on some level.

This is so damn sexy that it almost needs a NSFW warning.

Most of the credit needs to go to the original art/artist.  I was just replicating something else that had been done.   I really do love this one, though. That's the problem. I feel like I accomplished something and am a little scared to touch it.  So I bring it here to let those who aren't so infatuated pick it apart and force me to improve it.  I could easily just sit back and smile, but I feel like there is more room for growth here and I am totally okay messing around with alterations if it can improve the end result.  Nitpicks encouraged 
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Honestly, I can look at this and see exactly how my progress went.  I began with the farthest back elements and created them as I moved forward.  It's pretty evident that the layers became more and more in line with my own style choices as I came forward.

Architecturally, I had absolutely no plans when I created the buildings.  I started out trying to recreate from flash memory the original piece and ended up building this large castle thing.  I was aware of that bit of cognitive dissonance  between the light cast on the building and the placement of the sun, but didn't want to have the entire structure be shadowed.  The smaller building is also not planned at all.  I was thinking like a stable or something when I built it. My original buildings didn't even come close to matching in terms of era or style and I did some work to bring them closer together, but it wasn't enough maybe.

I am prepping an edit.  My main concerns at this point are composition oriented.  If I move the castle it won't be in the center anymore.  If I move the sun the lighting cast will work on the castle more but probably won't work so well on the foreground.  Those are the two most powerful segments and I don't want to lose too much strength in one to improve another.
The farthest layer of forest was made in that sort of bell curve in an attempt to draw attention to the castle.  However, when I started out I wasn't planning to make the castle so large and it probably doesn't require so much direct line focus to draw the eye.

I will rework the back line.  Play with orientation some.
Thanks with the comments.   

Quick Critique on the horse image:
To my eyes, the patches of lighter gray on the body seem off.  They appear to be highlights on the legs but on the main body those highlights seem placed incorrectly and/or at odd angles.
The seam on the horse's front leg is distracting and causes it appear to be "stuck on"
The horse's left rear leg (the furthest back) feels much more correct in form and length than the other hind leg. The abdomen feels like it narrows to a point really quickly there.

This was heavily inspired by an existing piece and I used the same colors.  But I would like any C&C on things that stand out as odd or needing work.
Each layer of my image was created by taking a quick glance at the reference and then creating my own version.  It was an interesting exercise in memory and tested my ability to capture the style of other artists.  I'm really not sure I came that close on any one element, but I really like this piece and want to know if there are any big mistakes I am not seeing.
The reference: http://i.imgur.com/OwAbieu.png
My recreation:

You can select an individual color and change it to another over an entire image with graphicsgale in several ways rather easily.
There is no need to redraw every tile and element by hand.