There may be a way to have server side skins without clients downloading client side mods, like mojang was going to do before they decided to cancel it. It would be very difficult but i believe its possible to by coding the server side files. We could be one of the few servers to do this 
Anyway i think i have found a forum thread that explains everything but eh, I'm not that good with coding but i can understand most of it. Ill sum it up down below. And koolio before you tl;dr just if you can take a bit to maybe look into this as it would be pretty cool to have a cracked server out a few couple that have this and cracked players dont have to have a steve skin. Idk its just an idea. You know me and my ideas To bad randude isnt here.
In minecraft source code, class "EntityOtherPlayerMP", line like
skinUrl = (new StringBuilder()).append("some url").append(s).append(".png").toString();
It loads in a multiplayer skins. You may replace url.
For example, as I have:
skinUrl = (new StringBuilder()).append("a seperate url to load the skins from like kraftzone.net/skins").append(s).append(".png").toString();
Skins are loaded from a/your web server. And players uploading their skins to the web server (kraftzone.net/skins)
For decompiling client and server, you could use Minecraft Coder Pack.
http://www.minecraftforum.net/viewtopic.php?f=25&t=58464
How to use:
===========
1) Prepare the files:
- Copy the "minecraft_server.jar" file into the "jars" folder.
- Copy the folders "bin" and "resources" from your "%APPDATA$.minecraft" folder into the "jars" folder.
2) Decompilation and patching
- Start the "decompile.bat" script in this folder.
3) Modding
- Modify the sourcecode in the "sourcesminecraft" folder or in the "sourcesminecraft_server" folder.
4) Compile
- Start the "recompile.bat" script in this folder.
5) Testing
- To test the modified game, start the "test_game.bat" script
- To test the modified server, start the "test_server.bat" script
For arguments sake i used iceAOS knowing she doesnt have a skin. (Dummy link btw)
1. Decompile client files
2. Mod EntityOtherPlayerMP to URL, where skins are like
3. Recompile
4. Reobfuscate (ensure, that there is Entity in client_obfuscation.txt)
5. Place im.class, om.class, qk.class from final_out to minecraft.jar
6. delete meta inf lol
Note that im not sure if the will even work, its merely hypothetical. If mojang can actually have a GOOD update. Heh as if.
:Minor edit- I think this would require everyone to provide a skin to work with their unique username on kz, alota work but just idk if it would single out the players that are already on the minecraft.net database then it could work. It takes alot of thinking...
I cant really build anything.
... this is what my skin mod has been doing for years now already. And it's one of the reasons the http://kraftzone.net/server login uses the ingame username/password to login, so that cracked players can upload a skin, because otherwise my server won't find a skin on mojangs servers for a player name that doesn't exist as a premium account. And thus the skin mod won't find a skin either.
And it will only ever be a client side mod that people will need to apply for it to work or use as part of a modpack.
Personally nicknames, and skins should be a hardcoded option in minecraft that lets users choose if they want to get there username and skin file from mojang or the multiplayer server they connected to.
That would be the best of both worlds and offer the best way of letting players have a custom skin per server (which would open up for server mods that could adjust a players skin for minigames etc), and a custom username on that particular server such as the username they really wanted but was taken globally when they signed up.
Just Mojang are stupid lazy and only listen to twitt feeders that don't give them any flak over there crap development choices.
(╯°□°）╯︵ ƃN∀ſOW <Mojang
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