If you want to use your skin as profile picture, youre failed.
Cause the "API"/Site you use to resolve the skin pictures doesnt support inGame names, it wants the UUID of the specific player.
Here you can see the failure about the failed profile picture http://prntscr.com/l0e424
The graphical Adress of this picture is https://crafatar.com/avatars/KleinDev?size=60&helm
It brings back an error -> Invalid UUID
So, the URL must must be set to this format: https://crafatar.com/avatars/cdf5ce70-079a-487b-8b71-b0ad4ffb4fb3?size=60&helm
But, if I placed my UUID (cdf5ce70-079a-487b-8b71-b0ad4ffb4fb3) on the profile edit page in the Minecraft IGN Section, it gives me an error cause its not an valid name. http://prntscr.com/l0e5dp