I think, any device or electronic independent accessory will need the CE certification. In case you assemble all devices together, a new CE certification is required.
CE marking might be ok for the board it self, but a CE approval does also require a EMC test / verification where the demands are different according to the end usages of the products. e.g. industriral or domestic. I you build the PINE64 together with other circuits might an new approval be required (if you want to put your product on the marked) e.g. if your stacking two PINE64 boards and adding a switch mode power supply will the RF radiation increase and need to be verified with an EMC test in a EMC lab before you can apply a new CE label to the product.