You can use environment variables to customize config (see docker run environment options):
docker run -v bitcoind-data:/bitcoin --name=bitcoind-node -d \
-p 8333:8333 \
-p 127.0.0.1:8332:8332 \
-e DISABLEWALLET=1 \
-e PRINTTOCONSOLE=1 \
-e RPCUSER=mysecretrpcuser \
-e RPCPASSWORD=mysecretrpcpassword \
kylemanna/bitcoind
Or you can use your very own config file like that:
docker run -v bitcoind-data:/bitcoin --name=bitcoind-node -d \
-p 8333:8333 \
-p 127.0.0.1:8332:8332 \
-v /etc/mybitcoin.conf:/bitcoin/.bitcoin/bitcoin.conf \
kylemanna/bitcoind