IMPORTANT: Long time has passed and now I am certain that developers don't care about forums and community suggestions. But you CAN implement random textures into your texture pack and clients with MCpatcher or optifine will see them. I made a tutorial a while ago but it is horribly outdated and I have no idea how it works now and I don't feel like updating it, sorry.
The idea:
According to my idea, there would be few different textures for every block (or almost every) that game would randomly pick when the block is placed or found already placed. Common suggestion was also to add random items too.
This should improve the way everything looks (especially with texture packs) and it would work similarly to random mobs mod that is already supported and used in many texture packs. Look below if something is not clear for you yet.
Scheme below is OUTDATED due to changes in 1.5 then later in 1.6 In fact it's easier implement with today versions
Scheme below is OUTDATED due to changes in 1.5 then later in 1.6 In fact it's easier implement with today versions

More pictures in the spoiler! 








Misa's Realistic texture pack with this addition:
Quote from Misa
Y'know, this idea has been a working feature of MCPatcher since mid-April... I've supported it in my pack since it first came out. I'm kinda surprised people still don't know about it at this point. Check the documentation on the MCPatcher thread under the information for texture pack authors. The random texture feature is under the CTM support (method=random). You can even give weights to the random textures so that some are more likely to randomly show up than others. Here's just a few examples of some of the stuff you can do with the feature:
Random textures on grass, tall grass, and flowers.
Random textures on stone bricks to make them look a bit less perfect.
Random mushrooms with a closer shot of some of the random stone bricks.
Random labeling on TNT blocks. (You can also use random textures to give fences unique art not shared with planks.)
All of the above screenshots were taken with only MCPatcher installed(no other mods), and my pack selected.
- I've found few replies in various posts about this, but I wanted more people to see it. This is only an suggestion so far, and i simply modified my terrain.png files.
- Mojang has already done something like this - mossy and cracked bricks in strongholds that add much more variation. And if any of you played Terraria, you should get the idea because variations between grass, blocks and everything else is also seen there.
- And since many of you mentioned, this could be optional, let's say a texture pack artist doesn't have enough time for this, he simply leaves all variants of block texture same.
You're welcome to send me more pictures showing how this feature looks in a texture pack of some kind. I'd post them here.
You'd really help if you post this banner into your signature!!! (copy-paste the code below)

[url="http://www.minecraftforum.net/topic/1020295-random-textures-for-blocks-adds-more-variation-to-minecraft/"][img]http://img13.imageshack.us/img13/4730/wertyui.png[/img][/url]
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+1 <3
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any help? it just had a red cross in the interface and when i clicked it it sayed something was wrong :/
Just like him if im not taking wrong...