BIP-110 narrows the rules. Small OP_RETURN of up to 80 Bytes are accepted by ALL Bitcoin nodes, including the malware Core V30+. BIP-110 blocks are accepted by ALL Bitcoin nodes at this point in time. Spam blocks with degenerated big jpegs are rejected by 16+% and growing number of Bitcoin nodes. If you are a miner would you risk your mined Bitcoin block to be rejected by the network and loose 3.125 Bitcoins?