So I follow the guidelines for header image size (2880 x 656), make sure it's under 1 MB, upload via theme designer, check it out via the preview function, am satisfied and save... and then it doesn't look like it does in the preview. It's huge, stretching far outside the header space. What gives? (Also, why is this discussion area not searchable? Or if it is, how? I bet I'm not the first person to have this issue.)
And for the record, I wasn't thrilled with the image appearing to be cut off at the top in the preview, either, but at least I was prepared for that.