Since the Forge API, Mods are very easy to install (simply drag and drop in to the mods folder)
As a server hoster we could realy start getting advantage of it. (We already doing it :3) what i have in mind is a Mod that dont even need to communicate with the plugin. it just need to read the costum Name of the Item and use the Textures for it.

What we give our users:

The Mod
A Badass Sword Texture namend BadassSword.png
A Config file.

In the Config:

BadassSword:
Nether Breaker
Doomsday
Badass Sword

What the user get ingame:
When he See's one of the listet sword in the config for example the Nether Breaker they have the BadassSword Texture! In theory we could create the illusion that we have 1000 of diffrent items and make the Game Feel even more like Diablo or World of Warcraft.

With Armor it would look like this!

HolyChestPlate.png // the texture of the armor
HolyChestPlate_icon.png // the Icon of the item

The Config

HolyChestPlate:
Holy Chest Plate
Gold Plate
Juggment Armor
Paladin's Skin

There's no way for us to modify the base textures of Minecraft, even through utilizing Forge (that I know of). It's a Bukkit limitation, as we're using Bukkit and CraftBukkit. Until such a time as there is a Forge and CraftBukkit combination out there that we could possibly use, there is no way that this could happen.

That being said, I like the idea and wish we could do it. However, it's not possible due to the limitations of Bukkit, Minecraft, and Forge.

I see, thats really sad. I thought it would be possible, like the Optifne featuere of random mob textures or Block textures. (that allowes you make new blocks with the Metadata of wood or sandstone) I was hoping you could simply check if theres something writen in the lore to change the texture but as you say its not that simple.

but well, lets hope for the future^^

The closest we can get in bukkit would be to send the player a texture pack like my other plugin. http://dev.bukkit.org/server-mods/textiles/. However alot of things are changing so who knows what will happen with the new api's and such.