Bukkit

15:44:10 [GRAVE] Could not pass event org.bukkit.event.player.PlayerTeleportEven
t to SpoutEssentials
java.lang.UnsupportedOperationException: All skins must be a PNG image
        at org.getspout.spout.player.SpoutCraftPlayer.checkUrl(SpoutCraftPlayer.
java:927)
        at org.getspout.spout.player.SpoutCraftPlayer.setCape(SpoutCraftPlayer.j
ava:1024)
        at me.skawke.spoutessentials.SpoutEssentialsPlayerListener.setPlayerOpti
ons(SpoutEssentialsPlayerListener.java:326)
        at me.skawke.spoutessentials.SpoutEssentialsPlayerListener.onPlayerTelep
ort(SpoutEssentialsPlayerListener.java:96)
        at org.bukkit.plugin.java.JavaPluginLoader$9.execute(JavaPluginLoader.ja
va:326)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav
a:57)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j
ava:453)
        at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:400)
        at org.getspout.spout.player.SpoutCraftPlayer.updateNetServerHandler(Spo
utCraftPlayer.java:1316)
        at org.getspout.spout.SpoutPlayerListener.onPlayerJoin(SpoutPlayerListen
er.java:57)
        at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.ja
va:270)
        at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.jav
a:57)
        at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.j
ava:453)
        at net.minecraft.server.ServerConfigurationManager.c(ServerConfiguration
Manager.java:133)
        at net.minecraft.server.NetLoginHandler.b(NetLoginHandler.java:121)
        at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:87)
        at net.minecraft.server.Packet1Login.handle(Packet1Login.java:70)
        at net.minecraft.server.NetworkManager.b(NetworkManager.java:226)
        at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:47)
        at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:6
1)
        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:537)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:435)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)

the server shows me these errors when a player enter the game and i have set a skin for him.

it seems to be not compatible with CB 1.1 R4..

i have CB 1.1 R4 + spoutplugin 737 + spoutessentials 392

You're using an image that isn't a valid PNG. Simple as that. ;)

java.lang.UnsupportedOperationException All skins must be a PNG image