First of all, hello to everyone here. I've been lurking here for awhile, but this is my first time posting. I'm looking forward to getting to know all of you. =)
I've been an artist for awhile (I guess I'm decent, definitely not great), but I just started pixeling a few days ago. I'm pretty bad at it. It's surprisingly difficult trying to cram so much info into so little space, and I'm having a hard time wrapping my head around it. There are some incredible artists here, so hopefully you guys can point me in the right direction.
I want to make a modest little platforming game, and I just started my first tileset. Even though they don't look it, they're probably around five hours of work all together. Like I said, I'm having some trouble figuring this stuff out, hahah. Here they are!

First cave mockup...just some floor tiles and some quick background tiles, really.

After crawling around in tunnels for a bit, I want to have the game open up into a giant cavern, to change the scenery for the player. The waterfall is supposed to be *far* away, even though it's impossible to tell from the picture. I'm hoping when it's animated it'll be more obvious; the water is going to fall very slowly, and I might use some parallax magicks for the lake the falls are falling into.

First one again, but with higher contrast on everything. Everything looked a little too gray to me. At first, I was thinking I'd have basically everything in the game be tinted blue, like the only source of light in the game was the ambient light from the blue rock walls, but I think that'd get boring to look at very quickly, so I think I'm just going to light everything with natural white light.
So...any help or advice would be very much appreciated. I don't think the tiles look
bad right now, but I don't think they look especially interesting, either. Any sort of help at all would be great, since I'm pretty much brand new to pixeling. Any sort of good cave/waterfall pixel art would be great too...I have no idea how I'm going to draw the cavern the waterfall is in right now...I'm imagining the cave walls getting lighter and lighter as they fade back into the distance to where the waterfall is, but I have no idea how I'm actually going to render that, and I can't find much reference for what I want to draw anywhere, since there aren't many super-giant caverns with huge waterfalls in the middle of them in real life, hahah.
I do have a few sprites done, too; the player's walk cycle, and a monster (slug thing) walk cycle, but I can't save them as gifs for the moment, so they'll have to wait...actually, on that subject, any recommendations for good pixellng programs would be appreciated, too. I'm using Graphics Gale right now, which I mostly love, but it doesn't have a HSB color picker, and I'm horrible at working in HSL.
Thanks again for anything you can offer me, guys. I'll be plugging away in the meantime! o/