<div class="form-group">
<div ... >{image}<div>
</div>
<div class="form-group">
<label ... >{label}</label>
<div ... >
{input}
{error}
</div>
</div>
<?=\yii\captcha\Captcha::widget([
'name' => 'captcha',
'template' => '<div class="form-group">
<div>{image}<div></div>
<div class="form-group">
{input}
</div>',
]);?>