I face a problem when changing the default image. I added two images checked.png and unchecked.png. and added two css classes for marked and unchecked. Only an unverified image is displayed, but when I check it, the image is not displayed. I changed the default buttons by doing the same steps below and it works well for buttons. But for checkbox this does not work (pressing Cls is not in checkboxfield). Here is a small snippet for your reference.
{ xtype: 'checkboxfield', ui:'plain', checked: 'true', action: 'didnotassisted_Action', id: 'id_assignment_didNotAssisted', cls: 'closeout-checkbox-unchecked', // pressedCls: 'closeout-checkbox-checked' },
CSS
.closeout-checkbox-unchecked{ background-color:transparent; background-image:url('../images/unchecked.png'); height: 44px; width: 44px; } .closeout-checkbox-checked{ background-color:transparent; background-image:url('../images/checked.png'); height: 44px; width: 44px; }
If there is any other approach to completion, please help me. Thanks in advance.
@Andrea, here is a screenshot of what I get after applying your code. 
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