sounds spoopy scary skeltals
just kidding, but maybe your account was compromised or someone else was on it/or using hacks in general to change it? Or maybe you were getting visions, triggered with the sight of a profile picture? It may or may not be telling you something, what ever you experienced.
Sounds interesting though. A few years ago I was playing Minecraft online and I know I have a strong password with all sorts of characters, and for some reason my skin was changing.
Just be carefull on what networks you use and who you interact with over the internet, some hackers are elusive or they are more present and they can be very much an annoying and frustrating hassle depending on their own mission and why they are hacking and changing things without your consent or knowledge
be safe! If something else happens and its worse, i would suggest looking into safer means of daily communication or looking into a VPN or internet proxy or what ever will provide a barrier between the network and your computer since sometimes there will be no server, and its face-to-face ( computer-to-computer )