PayPal: they charge commissions and, if you plan to sell many photos, to minimise those commissions, you may turn on Micropayments account. This requires 2 steps:

1) Upgrade to Premium account (this does not involve any additional fees). Log into your PayPal account and go to My Account, Overview, Account Type, Upgrade.

2) Click Contact Us at the bottom of the page in your PayPal account and request PayPal team to turn on Micropayments for your account.