your on a good way, but i miss something. can´t say what it is. but you´ve done a very well paint-job. i agree with micha about the banner. the background colour is too boring. so keep on.
I´m surprised about the low score, as this is a very neat paintjob on one of the best minis GW has ever made; I´ve just painted the guy myself, and you´ve done well; you could have chosen a better background color for the banner, and the base needs some work - the rest is just good