Highly customizable checkboxes and radio buttons
damirfoy.com
damirfoy.com
Those are my suggestions. Do with them what you may.
but that might be an outdated sentiment. (it's just a feeling after all :D)
Disabled state text should also be grey. (Currently, differentiating between unchecked and disabled isn't easy.)
'Line skin' unchecked state as an 'x' may mislead some people.