Not sure how happy Tarn will be about printing a potential 5 layers. For example Grass + Bush + Stockpile + Bin + Item. But I think he will be open to suggestions.
Only after I read that that the problem to "make it transparent" took form for me.
Before anything else, I do like stockpiles the way they are now,
completly opaque.
Im not interested to see what is bellow the items stored there since the item is occupying the tile in anyways.
If they can be used as an exploit to prevent saplings and bushes as it was an actual construction, well... I got to say that this is not the first exploit and will not be the last.
Either transparent or just borders are indeed good looking. However, as mentioned at the beginning of my post, it have a direct impact at the way the tile layers will be programmed by Tarn. If he does agree with that, well there will be a modification to something that endure for a long time without a touch!
Made some mock-ups long ago. ^^
It's 18 types btw: 17 base + 1 for custom settings.
And now im curious hehehe.
BTW
Those mockups are displaying some tree trunks that look interesting. Im Guessing right if I say that you are preparing bark variation to specify different trees?