Herbs
Clyde

Adds 15 flowers and 6 mushrooms.

Time Travel
Red_King_Cyclops

Adds in a craftable time machine that can be used to time travel to different time periods of Earth's history.

Wildflower Fields
mzs.112000

Adds a wildflower field biome to Minetest Game.

Magma
SuperStarSonic

Adds volcanoes, lava vents and new magma blocks

Alien Tools
chaosomnium

Alien Tools Mod for Minetest - adds Alien Tool, Shield, biome, etc

Generic moon of Saturn
Red_King_Cyclops

Replaces the default earthlike setting with a generic moon of Saturn.

Ancient Bones
karlexceed

Adds bones with loot to dungeons.

New Horizons
Hi_World

Adds 4 new biomes and TONS of new blocks!

My Treasure
Don

Adds treasure chests around the world

Advanced Biome Decoration Modpack
EmptyStar

A collection of advanced biome decorations

Lapis Lazuli
LNJ

Adds lapis lazuli ore, items and blocks.

Valleys Mapgen
Gaël de Sailly

A map generator with valleys, rivers, mountains and many plants.

Bamboo
AwesomeDragon97

Adds bamboo which generates in jungles and can be used as a crafting ingredient.

Archaeology
SkyBuilder1717

Adds an looting and API in archaeologing

New Biomes
Arkatron

If you like underground biomes, this thing is for you.

Quartz Geodes
AwesomeDragon97

Extends the Geodes mod with quartz geodes.

Randomized Map-specific Ores
Piezo_

Adds two randomly created ores to each world with varying properties depending on the world's seed

Ancient Ice Stuff
Robot10&Scheletor

Adds a new powerful ore to the game

morebiomes
mzs.112000

A simple mod adding a few biomes to Minetest Game

Easter Eggs / Ostereier
Ineva

Adds various coloured eggs for Easter!

Unstable Caves
M BLOC

Some stones may cave in if punched, making underground expeditions more risky.

Nyancat's heaven (reworked)
Hybrid Dog

Adds a nyanland in the sky

Kitty/Kitto Ores
nemokitty9

Nemokitty9's own ore pack. Includes Tools!

Fragments
Amaz

A mapgen with a goal, with things needed to advance to the next level.

Startest
Robot10&Scheletor

This mod adds several space stuff to the game.

Tac Nayn
GreenXenith

Adds Nyan Cat's evil twin, Tac Nayn (and a gray-scale rainbow).

World Borders
argyle

Add impenetrable barriers to the sides and bottom of the world.

Beautiful Boulders
regulus

Procedurally Generated Rocks with (pretty) Accurate Collision Boxes

Zinc
alerikaisattera

Zinc metal, used for making brass

Purple ore
X-DE

Adds new purple ore to floating islands and caves from height 200 to 31000.

golden lava
GigaByte

add golden lava

Obdy
Sires

Adds some pretty OP tools :)

Trucraft
mt-mods

An alternative crafting system done entirely in the world.

Spawn redo
cathaya7d4

Drop-in replacement for default/spawn for more third-party biomes

Sun Flowers
Hybrid Dog

This mod generates flowers which close their heads at night.

Noriel Sylvire's Minerals Core Modpack
Noriel_Sylvire

An API for automatically registering recipes, nodes and ore generation.

More Coral
Nathan.S

Adds coral in more colors.

Fly-B-Gone!
Hugues Ross

Hides butterflies/fireflies

treasures
ademant

Treasure nodes with useful items

Underground Survival Lighting
Arkatron

If you like underground light in survival, use this mod, it can help that.