dude u seem to picked this up alot faster than i did
that last screenshot has some really great textures growing on it well done
one thing to keep in mind that i still struggle with is that if u fill the whole screen with this detailed texture it really takes away from the effect.
that is what i meant by using the darkness to ur advantage in that u can have large sections of plain totally dark shadow areas and then just have bits and pieces popping out into the light here and there.
ur already doing it in that last screenshot and i think u can take it further with more interesting placement.
its something that is hard to see when ur face is right up in the pixels so take a step back and have another look, and keep another zoomed out view (eg 2:1) when ur working to keep things in perspective.
then mark out sections where it is filled with shadow and mark out some other areas where patches of rock will show.
doing this adds a "structural" feeling to things in that there are the large chunks of rock which are then broken into the smaller detailed bits ur drawing now.
u can have large sections of darkness with sparse lit areas where there is lava.
so once u imply some larger sections of implied structure u can upscale the cracks in the rock u have now and make them have lava flows and leaks that are a bit more epic and flow over the surface of the rocks instead of down a flat walls.
and keep in mind u can have some rocks around the edges of these flows which are lit from both sides by the primary (grey-green) light and the lava.
i think the kraken thing looks great u should develop it further perhaps with different colours.
im imagining it as a LARGE obstacle u need to stop and figure out how to get around/past it.
so u could have some rock structure which forms a large shadowy crevice, and we see just its eyes in the darkness with a few tentacles hanging out.
and if u go near it, the tentacles pull u into the darkness and its game over son.
IMO that would be scarier and look more interesting/professional than seeing it just sitting there.
the scale of it i believe should be relative to ur screen res but u could just rough something in until u cement that in (its hard to choose isn't it!).
i also really like that rock bridge u started on the left i'd like to see where thats going.
if u wanted to u could make it a one-way street as it collapses when u run across it.
regarding the background if u like the look of it u should separate it in 2 layers.
i think the back-most layer could be made into a large tile which repeats vertically and horizontally.
the closer layer u could do the same or u could break it down into a 32x32 tileset or something which would allow u to make larger pieces to brick together.
anyway i could rant all day so...