My review is here.
Dusk Desert
Official Review
Design/Gameplay - 3/10
..hmm... well... a lot of things can be said here.
Alright, so this was a decent level, but it had a lot of issues. First of all, those invisible vine blocks are just mean. Why are they invisible? I almost gave up when I fell down that pit. But lets talk about something else first. The NPCs. I agree with Turtwig, they were spammed. Now, the level was very cramped. There wasn't much room to move. Maybe if there was, we wouldn't be talking about NPC spam right now. Because I didn't have any area that I could dodge the NPCs, except on the floating section with all the backtracking and switch blocks... While we're talking about that, how exactly are they floating? Even for Mario, that's just not right. It was a decent-length level, maybe a little on the long side, but it was fine. You... uhh... kind of sticked to one theme... sorta. We were in a desert, then a pyramid, then some floating sand bricks... I got a little confused.
So anyway, why did you put that midpoint... where you put that midpoint? Chances are, nobody's going to go and get that. They'll either forget about it, or realize its not worth getting to. I personally just continued playing, even after it was available. (to be honest with you, I forgot how to get to it)
Our next subject is gimmicks. You had one. That's a step above some levels. But was it executed well? I don't really think so. You had to stray off the path to get a shell so you could hit a switch block that you couldn't hit as the player. Then you had to backtrack and get to the switch blocks that came on/off so you could continue. Backtracking isn't typically a nice thing, and it wasn't in a level like this. Also, you had to hit a switch block and make some sand fall so you could reach the path to move on. One complaint; where did all that sand come from? Think about that.
And the theme of this level? You called it a desert, but it my eyes, its some sort of funky pyramid. Adherence to your level's name is actually pretty important.
Let's talk about some more technical issues now.

You cannot get down here, even by crouching.

You can very easily turn this place into a 1up generator. Look at my life count. This is the place with the Pikachu generator, where you have to get a shell to hit the blue switch block that was earlier on in the level.

How does one make this jump?

If you end up down here, you're stuck. Period.
Graphics/Atmosphere - 5/10
This wasn't as bad, but it had its own issues. It was all mostly SMB3. That's good. But as with the design of your level, it's nowhere near perfect.
First off, the Pikachus change color when they don't have their... weird hat thingies. How does that make sense? Second of all, why do the Pikachu statues have spikes on their heads? Also, why did you make the giant shell... a... dead Pikachu? That's just creepy.
You also made some other bad choices. Let's start with this one;

I don't like the wood at all in this level. The colors of it just don't go with everything else. But it's pretty bad here. It's half floating on sand, which NEVER looks good.
The sand was also supposed to be piling up on top of the temple. Here, its floating.

If you're going to defy logic in this way, at least use upside-down slopes instead of a bunch of corner pieces. This just looks terrible.
I don't really have much more to say about this, except for a technical issue. The ? blocks turn into used blocks that fit with the tileset, but Brick Blocks turn into their normal yellow. An example is here.
Overall Score - 4/10
This isn't the worst thing in the world, but it needs a lot of improvement. This level shall now go in the "Average" subform.
And yes, I just said "shall".