I'm not sure, it feels a bit overkill implementing a full property system like the Gateway/Request classes have (especially since we can't use traits with PHP 5.3), when all other gateways other than Mollie simply return id/name for these two methods.

I did look at your `amount` and `image` properties, although Omnipay is supposed to abstract the differences between payment gateway APIs, and no other gateways I can find return anything other than id & name for their fetchIssuers/fetchPaymentMethods. I don't think we should add more properties to the Common classes until at least one other gateway supports them.

I don't think it's a good idea having `getAmount()` and `getImage()` returning associative arrays like that (it defeats the point of having accessors, you may as well just call `getData()` and iterate through the array yourself). If you want to have accessors for these properties, I think the best idea would be to keep your \Omnipay\Mollie\PaymentMethod class, but implement `getMinimumAmount()`, `getMaximumAmount()`, `getImage()` and `getImageLarge()` so at least the return values are explicit.

Thoughts?