Additional Information
Many Protocols have defined their custom frame format. For example, the SAE J1939 has a frame that has 12 byte payload shown:

Basically, you need a different API/protocol that works over CAN that can enable you to send a higher number of bytes. For example, On April 17, 2012, Bosch released an updated CAN specification, CAN with Flexible Data-Rate. This specification improves CAN performance by making two key additions to the CAN standard: increasing the maximum payload size from 8 to 64 bytes.