The Eternal Expanse

Well done! The colors and resolution put a nice feeling to it. Reminds me of the lava tubes I explored in New Mexico's El Malpais near Grants.
The lava tubes I explored had more evidence of flow marks and of peel-down structures, yours appear to have roof collapse features: no problem there.

The critique I have is above and behind to the left of the character. It is rather subtle as the roof shows a line that either shows a collapse scar progressing to the left into a higher lava tube, or it outlines a projecting mass. At least that's the way it looks to me.
If that area is a higher entry tube, then putting a light hidden behind the left edge would help emphasize that there is greater depth there... it looks rather ambiguous as it is now whether it is an illusion of another tube at a higher level, a projecting mass, or some other image problem I cannot tell. I've not been in such a tube with a confluence like that. Hope this gives you some ideas. Fantastic image in any case.