It says on the wiki page and in this question that you can change you skin online, but my brother actually bought the game and we just share it and play in offline mode.
Is it possible to do this offline? I've tried changing the char.png file, and it changes my image, but it also changes both of theirs and we all still look the same, and they can't see it.
When you say "play offline", do you mean you simply play the solo game mode? Or do you mean that you play without a net connection.
If you're playing without a connection to the internet, you won't be able to log in to your Minecraft account. Even if you've changed the skin associated with your account, when playing offline your skin will always be the default.
I think an offline name change is preferable to an offline skin change.
If the server you are running is online-mode=false, there are a couple of tricks to get your name changed. If you can add a skin to a registered (free) account and search for the name change method (which are many on this site alone and very useful) you might be able to match and get something there.
As an aside, offline mode can be achieved easily if you use MC Patcher - an awesome way to load mods and easy way to get your minecraft.jar all set up without opening and closing it manually. When you get it set and 'Patch' it, you can click test minecraft and auto runs in offline. From there it connects to offline servers just fine.
Anyways this method would seem likely to work on multiple machines (most likely LAN only) but try to get that name change, work it to an account registered and change the char.png. Hopefully this will work out, maybe would be good to not log into the second minecraft.exe with a verified account to avoid having it share the same skin.
Information found from here: How do I change player name in minecraft multiplayer in offline mode in Linux?
@SET /P IGN=IGN=
@java -Xms512m -Xmx512m -cp "%APPDATA%/.minecraft/bin/*" - Djava.library.path="%APPDATA%/.minecraft/bin/natives" net.minecraft.client.Minecraft %IGN%***
(by EdGruberman)
Copy + Paste to new applescript, compile, save as application, launch:
property user_name : "Player"
display dialog "Enter A User Name" default answer "" buttons {"Cancel", "Continue"} default button 2
set the user_name to text returned of the result
set UsrApp to (path to current user folder)
set UsrApp_unx to POSIX path of UsrApp
set MineScript to "java -cp " & UsrApp_unx & "Library/Application\\ Support/minecraft/bin/minecraft.jar:" & UsrApp_unx & "Library/Application\\ Support/minecraft/bin/lwjgl.jar:" & UsrApp_unx & "Library/Application\\ Support/minecraft/bin/lwjgl_util.jar:" & UsrApp_unx & "Library/Application\\ Support/minecraft/bin/jinput.jar: -Djava.library.path=" & UsrApp_unx & "Library/Application\\ Support/minecraft/bin/natives -Xmx1024M -Xms512M net.minecraft.client.Minecraft '" & user_name & "'"
do shell script MineScript
(by Nashroe)
The skin is linked to the account, so, no, you can't have multiple skins on the same account.
I didn't even know you could login with the same account more than once at a time.
You can "borrow" somebody's skin by logging in as them with no password and playing in offline mode. It will also work in multiplayer.
