You've got the darker tones there already, you just need to be more bold with them. Bring them farther. Take this pic into photoshop and mess with contrast... you'll see it when it happens. Take all of your reference material and mess with it first
If you give up an extra hour on refining, your payout in the end will be triple. Layer in that saturation and be more confident. This one needs dark greens and black to push the shadows way back, then lighter opaques to fill this whole piece with ink.
The truth hurts please if you could please give me any help and advice it would be greatly appreciated I am striving to be the best I can be sometimes I feel I'm struggling I keep trying different techniques but bit hard to do on paying customers
I believe this piece could use a ton more mid tone coloring. The contrast needs to be beefed up and saturation needs work. It's there and can be done, but needs work as it stands.