invoiceninja/app/models/AccountGateway.php

<?php

class AccountGateway extends EntityModel
{
	public function gateway()
	{
		return $this->belongsTo('Gateway');
	}
    
    public function getCreditcardTypes()
    {
        $flags = unserialize(CREDIT_CARDS);
        $arrayOfImages = [];
        
        foreach ($flags as $card => $name)
        {
            if (($this->accepted_credit_cards & $card) == $card)
                $arrayOfImages[] = ['source' => asset($name['card']), 'alt' => $name['text']];
        } 

        return $arrayOfImages;
    }
}