This is gonna be a sober reply since it is late. I like your piece, so i tried to address some things with this edit.
Overall it is really flat. This is caused by several things: the characters are standing on the same horizontal line, missing perspective, placement of objects to create depth, the overall lack of shading to create depth, and finally outlines.
There is a lot of noise which also blends it all together. there is no need to detail every coin, chain or scale. In addition to a lot of busywork it also distracts from whats actually trying to get attention, mainly the character interaction.
The main composition seems fine, i just rearranged some thing slightly to put it more into perspective, so it seems more like a location, adjusted some of the poses to try making it more dynamic. finally adjusted the colors to give it a warmer, more unified tone. yours was a lot of the same yellow/brown, grey and red.
you re-used a lot of colors, which is not bad, but i usually try to give certain colors a certain purpose, and only reuse them for that. for one it makes recoloring easier, and secondly some color ramps fit one material or texture, but not another. just something to keep in mind.
for the coin details, try to make them sparingly. create clusters of coins here and there, which admittedly i did a sloppy job off, but i think you'll get the idea. if you add gems and other details, dont try to hide them, make them pop out. its a fantastic world, so it can have fantastic treasure, right?
Overall the edit is pretty sloppy, which is partly due to the insane canvas. i'm sure you realised yourself how tedious it is

I'd suggest to try working on smaller canvas in future projects. it gives you faster results and more room(ironically) to experiment.
That said, i'm curious where you'll take this!
