Size: 640x480 pixels.
Image must respect this value exactly.
I do not know about your particular image ... but I am making the images directly from Metatrader (right mouse click on the space on the chart and select 'Save As Picture'):
uploaded by same pattren no sucess .
Your image is 1175x274 (and you need 640x480).I mean: 274 < 480
You can look at the image: