It is dependent on Jcow version and your template.
For exsample at this official site, we need to change bellows:

• common.js
  $("#jcow_top_logo img").css({"max-height":"43px","width":"auto"});
• style.css

  #jcow_top_logo img {
  max-height: 43px;
  width:auto;
  }

• style.css

  body {
  font-size: 12px;
  font-family: tahoma,verdana,arial,sans-serif;
  text-align: center;
  padding: 0;
  margin: 0;
  text-align: center;
  line-height:150%;
  padding-top:43px;
  }

You need to change above 3 of 43px at least.
I hope that this works. I do not check by myself yet.

foken @shigeru 95 months ago