I have no Idea if these have been suggested before. If they have been I didn't know, I am just suggesting.
Some dwarfs like obsidian, others like moonstone or jet, but I have never seen a chunk of jet big enough to make a good room, so I came up with these Ideas to better engraving.
Stone Plating
This is when you take a stone block, cut it into a stack of 10 plates, and use 5 of the plates to tile the wall. (It looks like the wall is made of the stone plates you used.) so the wall is changed into that stone type.
Once a wall is plated, it acts as if it was a regular smoothed wall of that stone type, so embedding it and regular detailing would be do-able afterwords.
Disadvantages/Requirements
1. It takes a stone block and it needs to be cut into tile.
2. Walls need to be smoothed before they can be plated with any kind of plates.
3. Fortified walls cannot be plated.
4. Detailed walls will be smoothed again if they are plated. (This mean they go back to being smooth instead of remaining detailed.)
Ore/Gem Embedding
This is the next step in detailing walls to the highest quality. You have a architect plan out the finished design of the wall, (I have this because I really don't see architects doing anything of value.) Then a Jeweler/Metalsmith comes in with a cut gem/metal bar and places it into the wall, Finally a engraver details the wall into the finished product.
Disadvantages/Requirements
1. This is very costly to use gems and bars on every single wall. It was meant only for the highest of quality rooms.
2. This detailing takes a lot longer to do.
3. The wall must be smoothed before this can be done.
4. This method re details a wall, so the quality of the details on the wall before the Embedding will be lost.
5. If the wall is mined out, you do not get a cut gem/metal bar back.
Engraving a wall with Gems or Ore in it
This takes a wall with a gem or ore already in it, and skips it right to the Embedded wall stage. THIS TAKES A LONG TIME TO DO!
Step 1: Architect comes a plans out the wall
Step 2: Mason comes and smooths down the wall (this dose not smooth the wall, just part of the process.)
Step 3: Metalsmith/Jeweler comes and cuts/hammers the ore/gem into a proper shape.
Step 4: Mason comes back and dose the finish Detailing. (This takes the longest.)
Like Embedding you cannot get a gem or bar if you mine out the wall afterwords.
Few Side Notes
I TRIED to make this a lot like Fortifying, so maybe embedded walls can be fortified. Something I know a lot of people have complained about.
Yes, with this a person can make a inf supply of jet using the plating then mining it out. (In my head it turn the entire wall into that type, so when you mine you end up with a jet stone if you used jet plating, if Toady can get around this then I would be VERY happy, but I don't want to make things more complicated then it already is with this.) But you already have an ENTIRE MOUNTAIN of stone! I have NEVER run out of stone, and with Z-axis coming, you wont either.
I do think that people could have the same problem with plates that they have with coins, but these are not stacks of 500, its just 10. and unless you really go at this, I don't see any reason to have enough stacks of plates to have a problem with them being scattered.