Beleve it or not, I hardly mine in Minecraft. And I bet you barly do to, once you have collected enough diamonds.
Ores for the Crafters! - As you know, ores are the base item to create tools (Besides sticks) and are used to differenciate the powers of each tools and such. Anyway, if you haven't already noticed, their is a MAJOR dip in power when comparing Iron to Diamond. And I was thinking that new ores can possibly remove such a big gap.
Possible ore types:
Ruby: As of 1.4, minecraft still has the textures for the Ruby, wich was the precursor to the emerald. I think that rubys could be another currency, or even be stronger than iron, and still weaker than diamond. (Being closer to iron). (Requires Iron to mine)
Topaz: Being many colors in real life, Topaz could be a pink ore. It would be closer to diamond. My idea is that it lasts almost as long as diamond, but as strong as iron (Speed of mining and attacking). Plus, its humorus to be running around with a pink sword. (Requires Iron to mine)
Amethyst: A more purple ore, and more like gold. Not in a bad way ither. Since in Minecraft, gold has a better chance to get better enchantments on it, that would be the only simularity. It would be slightly weaker than iron, but has the perk of enchantments. However, being as rare as diamonds. (Requires Iron to mine)
Olivine: A light green ore, and can be used for tools, unlike emerald. These green tools would allow you to have faster sword swings and faster mining speeds, however it will be at a cost. The ore will be at stone stength and will not be able to pick up anything that requires a iron pickaxe to mine. (Requires Iron to mine)
Use more Alchemy! - Alchemy is very under used and is said to be expanded apon, These are my ideas. They aren't fool proof, as I am not sure what minecraft is able to do and what it is not able to do. Proof of consept people! Plus, I like creating potions.
Alchemy will have a major role in this idea as well. All of the above ores, and default ores should now have a reason for them. I will list below.
Coal/Charcoal: A 'makeshift' use of Redstone. Increases 1/4 of the time compared to Redstone, can be used up to 2 times during brewing. Can be paired with Redstone to get 1 1/2 of an effect.
Iron: Can be crushed into Iron nuggets (similar to Gold nuggets) and used as a upgrade for potions. This increases the 'weight' of the glass bottle when thrown. More for traps, or if used with a fermented spider eye, reversed and makes it be able to be thrown farther.
Emerald: A primary ingredent, Allowing for better trades. Brewing this will create the 'merchant potion'.
When trading, you will get better deals than normal, and will have a higher chance to have villagers give you more trades.
Lapis Lazuli: This ore can be used to replace Nether Wart. Yes, that is right, that valuable material to create potions. This is mainly because lapis is very un-helpful. But there is a catch, it only creates potions equal to 1/4 of the power of a normally created potion.
Diamond: A very pricey potion to make, but instead of upgrading, it becomes a full ingredient. When brewed, it creates the 'invinciblity potion'. It makes you a walking tank for 1 minute, and up to about 4 minutes when mixed with some Redstone and 2 Coal. Upgrading it with a fermented spider eye will make it a Instant death potion, and Glowstone dust will make it into a larger ranged throwing object, and will make it so if you are hit with the invinciblity potion on you, it damages anyone who attacks you.
Ruby: This is a ore that will allow for mining help. Brewing a potion using this will create a 'Miner's potion'. It will, over time, tell you if you are near ores. A level 1 potion will detect ores 6 blocks away in any direction. A level 2 potion will find ores in a 10 block radius. And if level 3 is possible, 14 blocks. Note, this will not tell you what the ores are, it will only notify you of close ores.
Topaz: This will create a potion already in the games coding, but not accessable. Blindness. That is all.
Amethyst: With this special ore, you can COMBINE potions. That is right. Creating a 'Mixing Potion' will not allow you to eat it, or apply gunpowder to it (throw it). It will then allow you to put another potion in the top brewing area, and then you can create even more potions! Brew blindness poison potions!
Olivine: It allows for haste potions ingame without cheats. Nuff' said.