That's a pretty good start. I quite like the eyes.
Darklining is in order to help separate some of the elements in the mini. The cigar for instance, would need to be much darker where it meets the mouth, so it doesnt look like he lit is own tongue or something like that.
The blue flame and blood splatter are good ideas, but it needs a lot more skill to make it credible. I think blue flame would be a lot harder to render correctly than red flame.
Metallics are the real low point here, which is very normal, it takes most painter a while to get them right ( I still often struggle with them); until you find your way to deal with them, you may want to avoid putting too much when it's possible, like having large parts like the 'barrel' painted on instead of metallic ( Which would be in character with orks imo) and using more gunbolt metal than silver, which doesn't show flaws as much.
And doing the base would be next, it is also a lot of fun
Mind, this is all only constructive criticism, which is the point of the forums, the most important thing is that you enjoy what you do.