Battlelog has recently added many changes into the emblem editor, and now the canvas size of the editor is 512(height) x 512(width). BBLog 4.7.0 still uses 320x320, so 512x512 canvas support needed.
For example, an overlay image is shown as 320x320.
EmbEdit-canvassize1.jpg
BBLog version: 4.7.0
Browser: Firefox 36.0.1