It would be nice to see more mineral deposits that give decorative blocks instead of ores. Igneous Rock deposits, as well as prismarine and blackstone being available from ore deposits makes the addition of more not entirely unprecedented. Some suggestions for deposits would be:

Geode Cluster:
-Amethyst, Calcite, Smooth Basalt

Permafrost
-Ice, Packed Ice, Blue Ice, Snow Block

Hematite
-Iron Ore, Red Sand, Red Sandstone

Fossilized Seabed
-Coal Ore, All variants of Dead Coral Blocks

Bioreserve
-Moss Block, Spore Flower, Rooted Dirt, Azalea

Sculk Tumor/Growth
Sculk, Sculk Sensor, Sculk Shrieker, Sculk Catalyst

Nether Geode
Obsidian, Crying Obsidian, Glowstone