Is your feature request related to a problem?
There is only one way of generating veins

Describe the solution you'd like
Different patterns of ore spawning such as:

• Centered distribution
  • Like Lapis Lazuli in vanilla, where most of the ore spawns at the center (or maybe a configurable position) and peters out further from that spot. Stopping completely at the min/max heights
• Spheres/Ellipses
  • So we can make boulders, discs, and/or oval shapes of ore spawning. Discs/planes could be great for making layers in the ground simulating things like crusts. While boulders are an aesthetically cool shape which could fit rock themes well
  • Plates/Cylinders is a better way to describe the axial plane idea, round shapes with flat top/bottoms, optional tapering would be nice (possibly consolidates spheres/ellipses/discs into one pattern, just different radius1, radius2, height, true/false tapering).
• Geodes
  • Imperfect ellipse shapes which have a crust (small variations in height/width to give a natural look, also further differentiates it from the above idea)
  • Having a crust makes for some cool encounters, you could for example always surround an ore with lava, or surround ores with obsidian, or surround liquids with solid blocks, creating underground pockets
  • this would require picking a crust material separate to the ore and filler
• Fractal
  • gaps between ores in a fractal like pattern. Similar to normal veins but spread out over a larger area with filler inbetween the ores.
• Other possible ideas are things like trees (pick the trunk/leaves, spawns on top block between min/max height), decorations like plants/blocks in 1x1 that spawn on the top (filler, only if one is found, like grass) block between a height range

Describe alternatives you've considered
There's not any alternatives that I have found in 1.16

Additional context
here's some screenshots with geodes and discs/planes

Mostly Discs, some are sliced in the walls

Some geodes in this one, some are cut in half

I'd add Railcraft's "cloud" to this. Dense core with less and less ore toward the outsides. Plus, the ability to specify some kind of "marker" up above (e.g., a boulder which pieces of the relevant ore, or a certain kind of flower planted in a dense bunch).

I'd add "spouts" to this list. These are pretty much the same thing as the original BuildCraft oil wells. It starts with a geode shape deep underground with a vertical shaft up to the surface. The liquid fills the geode and the shaft, and extends upwards to form a tall spout above ground.

Moving all feature request to discussions:
#64