The Bruce in the banner is made by colorreducing a photo and then overworking on the pixel-level. That's about what you 'can't do'
The issue is always stating what you did, not wether you can or not. However at your current skill level, yes, working from reference but eyeballing things and drawing them from scratch yourself, not letting the computer color-reduce would help you much, much more. And people would see the effort involved and be more willing to help.
Right now, though the piece is a bit sloppy in places, it's consistent, but that consistency is on borrowed strength: the volumetrics and lights are pretty good, and that's because they're from a picture. If you took that away from it, you'd have a clearer representation of your current skill level with pixels, and therefore people would be much more able to help you with your actual shortcomings, not shadowed by an illusionary control of volume and light.
