Asus made a crypto-mining motherboard that supports up to 20 GPUs - The Verge
Amazon.com: BITEO B250 Mining Motherboard Boot Up Mining Support 30/20/10 Series GPU 12 PCIe X1 to PCIe X16 with CPU mSATA DDR4 VGA DVI-I for BTC/ETH/ZEC/ETC : Electronics
Intel/AMD Crypto Mining Platform|Mining Motherboard line up-Biostar