Well it's not going to be a cover illustration. This is for a screenshot in my series about the Breaking of Forstor Nagar project I'm involved in. The screenshot will be up on Monday (but for those who want a sneak peak it's here: screenshot) Note that not all of the art there is mine. The tokens are Devin Nights and the portrait of the warrior is by Tyler Bartley.

However if I were to truly want to polish this - do you have suggestions?

As for the photoshop issue - not only is it all PS, it's all done with a hard round brush. Probably what I use 99% of the time these days. The shades are all done with layers set to soft light and built up over a textured background.