I really love the texture for opals as well as the other gemstones, but opals especially. I find it really sad though that there isn't really a way to decorate your base with them except via picture frame and opal blocks (which just aren't as cool as the single stone).
I would like to suggest then, a system of decorative blocks centered on gemstones and other precious metals.
I think it would be cool if a player could craft various settings for gems. For instance a basic gold setting would be four gold nuggets; it could then be craft with any gem and then able to be placed in the world. The block would be more 3-dimentional than a gem in a picture frame but still look like the single gem, just fixed in some gold. Multiple settings or additional metal items could be crafted to make larger decorative blocks like statues or jewel encrusted pillars or pillar caps. There could maybe be a way of making gem settings that give off a bit of light like the dwarven inventions that captured light in stones to be used in the mines. Or if crowns could be crafted and given gems or thrones or lanterns or other decorations. Different factions could have somewhat different variations to more closely suit the level of skill associated with a given faction. (Elves would have bright elaborate styles while orcs would be rough and dirty)
It might also be fun if gems could come in different sizes which would in turn affect how they could be used in crafting. For instance, a raw opal block could be broken and either drop one big opal, a couple medium opals, or several small opals. Larger gems could obviously be cut into small pieces but smaller ones could not be recrafted to larger ones so players would have to plan for that. Maybe specialty mining tools could be made so that there is a higher chance of larger gems.
It just seems to me that there is a lot of potential in the game's gems for some great decorations that would really add a lot of life to structures, especially castles and such.
I couldn't find any posts similar to this so I apologize if someone has already suggested this.