Frazetta is a the man, a great collection of his work can be found at frazetta.org
His pieces are inspiring my “death of a tribal” piece (currently on the last page of my sketchbook)
On quick glance, I’d say you need to bolster the muscle in his arms, and really identify the strangely unique shape of his abdominals. Your arms need to be turned in slightly more to really get the striation of the shoulder in that pose, it makes him look much more barbaric. also watch the size of his chest cavity. His rib cage in the painting does not protrude as much. In yours the pectorals dominate his upper frame. Frazetta was known to swap in ape anatomy for humans, pushing the barbaric and animalistic nature of the pose. whilst remain grounded in nature. I’d study some gorilla poses for this one. also his rig cage appears a bit wide.
As for the woman, done be afraid to make her meaty, beyond large breasts. Frazetta’s women were curvy, and rightfully so. give that girl more of a gut and booty. As odd as it seems itll balance the breasts, giving her less of a porn star like look.
I know thats a lot, but If I didn’t care or think you could do it, I wouldn’t have bothered writing. You can really make this piece really special and I hope you do. Its looking really nice so far. just push it that little bit more