This is a weakness of mine that I'm going to have to address in a coming project. As such, time to start practising!
Tonight's effort:

Quite happy with the stone squares, less so with the grass tile. I'm not sure whether to revisit it or move on with lessons learnt which are:
- The grid is tricky to get rid of at 32x32 (something I'd forgotten after doing so much small scale work). I'll have to explore some more reliable elimination strategies.
- Drafting first is still handy - scribbling details at 4x scale and then scaling down still works wonders for getting the initial form working right
- Making "sub tiles" is a great idea for inorganic stuff. I made a few smaller chunks of stone and tweaked them in some of the larger tiles, adding moss and whatnot. This is very handy because it provides some semblance of structure as well, but does cut down variation. I should rework the lit edges at least.
- More colours help a lot at this scale - I was endeavouring onwards with my usual 3 tones but adding colours for highlights helps details pop a lot. Hi res tiles do well with a hi res palette
I'd love some criticism. What works, what doesn't, what should I bother fixing in this piece. Are there some clusters that really bug you? Are the tiles arranged stupidly? Should I get some unifying greys into the grass tile?
Edits appreciated, I'd like to get more adept at this size as I'm not as quick as I'd like to be (yes, I'll eat my words from the payment thread soon enough.) These were done in ~2 hours for what its worth, with half an hour or so wasted at the start.
I await your critique.