Ducktopia.
Sprite quality: B
Parallax Scrolling: B
Special features: C

The quality for the sprite is good. Not tremendously reallistic as I prefer but gets the job done. Except for your statue, the building and columns are really flat. Trees are good, but the ground is way too plain (I don't blame you tough, even now I don't know how to make realistic grass floor on LF2).
At first parallax scrolling seemed flawless, and pleasant to the eye giving a good depth. Then I noticed that the columns/second grass layers move mindlessly. They should move with the same width. Also, the trees get smaller and smaller but they don't move accordingly.
No special features except for the water animation and the transparency of the rainbow that are not specifically hard to do.

Acherontic.
Sprite quality: A
Parallax Scrolling: B
Special features: B

Out of the made from scratch backgrounds Acherontic is one of the best regarding sprite quailities, even though it's way too rough on some places. The ground is specially good, and I say it because I know the fight ground itself is hard to sprite. Also I like the color palette.
Talking about special effects, the skeleton was a nice touch, but I think it's way too large to be a LF2 char's skeleton, and it seems to me it's supposed to resemble that. The bridge was also a good idea, but could be executed better. I mean, it's way too small, I noticed it because I knew it was going to fall down. Some sounds for it would help.
The worst aspect of the background is, in my opinion, the parallax scrolling: the width of the trees on the left are ok, but the mountains, judging by their size in comparision with the chars, should be really far. Parallax scrolling says otherwise. For example, the city/citadel wich is a main point of the background seems like a miniature some meters behind the chars. That killed the depth of the background that I perceived from the screenshot in the other thread.

Julian's Cave.
Sprite quality: B
Parallax Scrolling: A
Special features: C

The sprites don't have many flaws but lack technique. I like the columns specially. The statue is really flat though, and the texture in the ground just doesn't fit. The animation for the cascade needs more frames and more quality.
Parallax scrolling is fine and pleasant to play.
No special features except for the cascade wich needs work.

Scientist's Lair.
Sprite quality: B
Parallax Scrolling: C
Special features: C

This had some much potential sprite-wise. I like what's finished (the injured guys, the scientist and the monkey specially). It's really disappointing that some things seem unfinished. The worst of this background is the perspective. It is totally wicked. Just from the start I had the feeling that the whole wall was gonna fall on the characters... I'm not sure how to explain it... but never do the floor like that. It kills al perspective. Look at the monkey's cage base, that's how the floor's lines should go.
No special features/parallax scrolling. The animation is there, but not enough for a B.

Vallenfyre.
Sprite quality: A
Parallax Scrolling: C
Special features: C

What can I say from these sprites? Awesome? The resizing is good and there are almost no flaws. In fact I detected just one: if you go to the top of the zboundary in the center, the fighter stand on irregular blocks. A 10px correction should be enough to solve that.
Sadly it has no parallax scrolling or dynamic effect.

Sunset at Marina.
Sprite quality: B
Parallax Scrolling: B
Special features: C

The fighting ground looks good. The sunset in the background has good colour but lacks technique... just using the smudge tool isn't enough these days. You could add clouds. Also water could be animated. This BG has potential, but you should add more things.
The parallax scrolling... I can't say it's bad, but there are just 2 frames, right? And yet again no special effects.


Crystal Cave.
Sprite quality: B
Parallax Scrolling: C
Special features: C

The spriting looks rough on some parts, and very smooth on others (in the bad way), but you're improving. I know it's hard to do such large things. You'll get better with practice. Try to use a 3-2px brush to sprite the rocks, no exceptions: there's no easy way out of it if you want perfection. The animation could have more frames since is such a lighting.
Ok, what's happening with the parallax scrolling here? It seems like the fighting ground is moving along the players... that's completely wrong. The width of the background must be the same than the width of the fighting ground layer. That means you have a lot more of floor to sprite (around 400px) :D
No special effects.

Troll's Awakening.
Sprite quality: B
Parallax Scrolling: A
Special features: B

You're in the right track trying to sprite rocks manually. It's painful, but it's the only way to make it look good. That frame in the back is the best. The one in the middle, is too smooth to be rock, and the shapes are strange. The fighting ground: just using a granite texture isn't enough. You have to do the same thing you did in the last frame, but much more subtle and with a different perspective. All in all, in the right track but lacking more technique. Oh, and what's with the sky frame? Are those rocks flying or clouds? If they're clouds, the perspective is kinda wicked. If they're rocks, it needs animation.
Good parallax scrolling.
I like the special effect. The animation could really be improved, and you should add sounds.

Toad Stool.
Sprite quality: A
Parallax Scrolling: B
Special features: B

I really like the sprites used in these, even though they are not manually sprited from scratch. Also the blurring puts special attention on the fighting ground rope, and gives the feeling of being a small insect or something. The sprite of the boss screams Chishio, but don't really fit with the rest of the sprites. Also, it disappointed me that only one half was done and then horizontally flipped...
What you tried to do with the parallax scrolling in the background is interesting, yet not enough to be good in my opinion... maybe add more frames to give it even more 3D effect? Appart from that, no parallax.
The special feature is also really interesting. The fact that you have to fight a boss is awesome, they way it appears and the effect of its wings are also good. On the other hand, it completly kills the AI in almost every match I played. Every CPU player just keep walking to the other side and does nothing... even if that is intended, I don't like it. I know it's impossible to make the AI attack the insect, but atleast let it keep fighting you. I didn't like the extremely small zboundary gameplay-wise. The first time I saw it I said "Nice!", but after playing 30 seconds I hated it, specially with the insect boss.