As cryptocurrencies are more and more popular, you may want to allow your customers to pay with Bitcoin, Litecoin, Dash or other crypto. Here are two examples of payment gateway services, that will allow you to easily implement cryptocurrencies in your store with their free Prestashop module. There are also standalone paid modules available on official addons portal, that allows to accept Bitcoin, Litecoin or Bitcoin Cash, without any 3rd party.
Supported cryptocurrencies: Bitcoin, Litecoin (in Beta)
Prestashop module on GitHub: https://github.com/bitcoinpay/bitcoinpay-prestashop
Bitcoinpay currently supports Bitcoin and Litecoin in Beta. There are no monthly fees, the transaction fee is 0.8%. It allows to instantly convert the payment into your local (fiat) currency and every payment has it's invoice in fiat, so there is no problem with accounting. Payments are deposited into your linked bank account or wallet each business day according to your preferences. They also have solution for retail stores - web based Point of Sale for mobile devices and more advanced App. LILKA Point of Sale.
Supported cryptocurrencies: Ethereum, Bitcoin, Litecoin, Bitcoin Cash, Bitcoin Gold, Dash, Ethereum Classic
Prestashop module on GitHub: https://github.com/Paybear/paybear-prestashop
PayBear is quite a new project, they are going to have crowdsale, but they already have working product in BETA stage with impressive list of supported cryptocurrencies and more to come. Because of Beta stage, fees are 0% at the moment, you only pay the sending fee to process the payment in the network. In future, there will introduce some fees, existing users will be notified in advance. Payment is sent directly to the merchant's payout wallet. In future, they should also support Crypto to Fiat and Crypto to Crypto conversion, according to their roadmap.