The thumbnail is black because you saved the image as PNG; even though you changed the extension to JPG, it's still encoded as a PNG image. Anyway, I've fixed it for you now, but just letting you know for the future to export or save as JPG.
and yay it's Mwu! and I thought I was the only one who vectored him XD I like how you put his feather emblem there on his name, though the background purple is a bit bright...
would you like to join 
?