Paladin 20 (From Smite to Song feat, CoV, effective bard level of 20) = +4 Inspire Courage
Song of the Heart (feat, Eberron ACF) = +1 IC
Inspirational Boost (spell, Initiate of Milil feat, CoV) = +1 IC
Badge of Valor (magic item, MIC) = +1 IC
Battle Rattle (magic item, Dr#331) = +1 IC
Word of Creation (feat, BoED) = x2 IC
Balance here could be totally disregarded if I include Masterpiece Performance (Dr#301)... but yeah.
So... Total of +12 OR +16 if you do double everything with WoC, so +12d6/+16d6 (42/56) fire damage with DFI as a Paladin. Problem is few uses per day. So few smites/day..
I'm not sure if Initiate of Milil helps the number of uses per day? At first I thought of Devoted Performer for this but I guess it doesn't work..
And then there's that Inspire Courage from Harmonious Knight. It is technically not bardic music so most things above doesn't help it at all.. Song of the Heart does though, since it doesn't specify bardic music inspire courage, but that's twisting words around.