It could be whatever site you have it hosted at (assuming you're hotlinking it and not uploading direct to ECF). some image hosts will re-size during upload and others will only hotlink a thumbnail. If you have it hosted externally and the image you uploaded is larger than what is displayed, try using a different host and see if that helps
EDIT: if you aren't hotlinking and had uploaded the image directly to ECF, then this doesn't apply, of course