I haven't seen such a graph, yet. So I made one myself:
http://bitcoin.atspace.com/fees.html

The fees are still fairly insignificant (only about 0.04 BTC or 0.08% of the 50 BTC) but has gone up from zero. The first jump in fees was related to the start of fee inclusion by the Faucet. The Faucet has recently started to group the transactions to minimize the fees but there is a pickup of fees probably paid by 0.3.21 clients (low priority transactions).

I wonder how large will the fees be at block 200,000 when the payout drops to 25 BTC.