After some talk with Coinpayments.net they have decided to add Blackcoin!!
If you find a store accepting Coinpayments but not BC, ALWAYS send the store an email to start accepting it.
https://www.coinpayments.net/supported-coinsMore information will follow from devs.
Regards
Jilixi
+1000
Update: CoinPayments.net has been sold to a trusted member of the Bitcoin community, Cycloid. His team will be running the site by March 31st and CoinPayments will continue operations without any interruption.
It will be interesting to see what Cycloid does with it in the future.