*Slaps self in face, make sure you re-read the whole thing again before editing*
Okay, not sure if this is exactly what you were looking for, but this is what I have anyways. I thought the tiles below yours were yours as well, since they were part of the scene, but it might help you anyway. And, aren't you allowed to break the grid a little if done well right? Right? (Maybe the other guy won't kill me for editing his tiles.) Okay, moving on.
I've divided the edit parts into alphabetical and numerical sections for easy explanations. So. First on the list, section 1a. Added a bit more of a shadow to the ooze crater and the alien pool to make them stand out a bit more. The red bits in the crater is where a lava pool had once been. I'm sure you can make the transition smoother. Perhaps smoke coming out of it? Next I added a third trail going down from the crater to the south-east(?) part of your tile to were the gray piece of shrapnel is. Then I have it dripping down and merging with the lava flow at the bottom of the part. This was mainly to show how the green bubble got there, and how the two fluids merged with each other using subtle shades. (Which, is section 2 btw.) Also, a minor note. The rock at 1b didn't seem just right. So I kind of "finished" the shading on the bottom.
Now the glaring part of this piece. I think I know what your trying to do with Section 3, but either don't want too, or ran out of "time". So, here's my take on it. When Dusty said he didn't know what was going on with your piece, he was right. If that's supposed to be a crash site in the side of the mountain, well. Where's the debris, shrapnel, burn marks, smoke, jagged rock pieces that make a crash site what they are? So, I thought, okay, maybe not a crash site, but a crash into an already existing cave. Specifically, the snakes cave. Which would explain why he's so ticked off.
So, in order to create the feeling of a cave opening. I moved what I assume to be the main debris over a little. Then I took a section of your overlap at the south corner and used that as an overhang. Then I added two shadows underneath to give it a bit of depth. (Maybe a bit much.) Finally, I gave the overhang some light shadow on the top to kind of give a merging of the two tiles. Oh, and if your wondering if it looks a bit odd or out of place. It's cause I copied the cave opening with the ooze coming out of it to use as a base. All right, on to section B.
I was worried that I had edited the wrong tiles, but I guess not. Phew. All right, I was unsure of how you wanted the ooze to merge with the black, but I thought the area needed some more work. Like I did in section 2a, I merged the ooze with the rock a bit more to give it some more character. I also thought that would give the idea of a merger that you want to try and get across. I gave the stream of ooze two colors. Just so that it matches the contrast of the surrounding rocks. Also, is that grayish shrapnel piece supposed to be your snakes origin spot? I thought the hole was a bit small. So in section 2, I moved the shrapnel up. Then took a surrounding rock piece and put it as place holder. Then made the hole a bit wider so as to make sense. That's the only things I see there mainly. Now, on to the fun part.
I reserved section C to show what you could do with the snake. The blue circles are entry and exit points. I think it'd be a bit fun to have him going behind the mountain a bit. He does have a nice selection of busted ufos on him. Maybe you can add more or less depending on your preference. Since he was in the path, I also have him killing the black cloud creature.
I love pixel art, and good pixel art at that. I'm not sure if this is what you wanted or not. And I hope I can take a critique (if this isn't a nitpick) like this when I get this good. I hope I helped you a bit and can't wait to see the finished piece. (However, if you want, you could call it finished as is. I just pointed out some spots that I thought what you thought needed fixing.)
