No part of the face or head should be covered.
YOU know what the person looks like but we don't - and we'd rather NOT guess.
It's okay for someone else to be in the picture, so long as we can still see your "victim" properly.
If your "victim" is wearing glasses, shades or a hat in your photo, they will be in your finished cartoon, too.
If you want us to include something specific (like a uniform) we will need an extra photo showing what it looks like.