I'm not really a modder but I understand some of the basics.
Why would it not be possible to do it this way then...
1. Mine stone, let's say Conglomerate.
2. Convert stone into decorating stone at a smelter. (reagent: stone, produces a metal bar, entity unique by stone type) Say, Conglomerate rock into Polished Conglomerate.
E.g.
[REACTION:POLISHING_CONGLOMERATE]
[NAME:Polish Conglomerate]
[SMELTER]
[REAGENT:1:STONE:NO_SUBTYPE:STONE:CONGLOMERATE]
[PRODUCT:100:1:BAR:NO_SUBTYPE:METAL:POLISHED_CONGLOMERATE]
3. Include entries for all decoratable stones into the matgloss as a metal bar. Polished Conglomerate would have to be a metal with no actual ore assignment.
E.g. [MATGLOSS_METAL:POLISHED_CONGLOMERATE]
[NAME:polished conglomerate][ADJ:polished conglomerate][COLOR:7:3:0]
[VALUE:3]
[SPEC_HEAT:450]
[MELTING_POINT:14000]
[BOILING_POINT:18000]
[SOLID_DENSITY:8800]
(I used the metal entry for Nickel, you'd want to tweak these better and assign colors properly)
4. Use said Polished Conglomerate in a forge for decoration.
You can assign the reaction to not use fuel (I believe) and decorating at forges doesn't use fuel already. Sure, you'd have metalworkers decorating with stone, but Footkerchief's idea is valid. Actually doing it... don't know. I've provided examples but I don't know if they work. Like I said, I'm no modder, but I think it should be possible.