Tip: You can use Lunar Magic's Overworld Layer 3 Editing system to edit or create your own layer 3 images (castle bricks, fish, rocks) and apply unique effects per level via the Layer 3 Bypass in the main editor.
Ok, nice block and all but please consider a few things from now on.
As Vitor said, you don't need to "update", "re-update", "update 2" and whatever as your blockname. We can tell it's an update simply by the obsolete field which gets filled if you use the "submit update" function.
I removed the mwl file because it is blood unnecessary. For submissions like your screen scrolling pipes, I can understand and appreciate including an mwl file, as it helps to clear things up. Here though!? All it does is one screen showing the two blocks being placed in a level. I honestly don't think you have to state the obvious. If it was for some complex exanimation then maybe, but we're talking about a two frame long animation here.
Your god damn readmes. Look, it's great that you include a bit of an "howto", but when your readme is longer than any of your ASM files, you're doing something wrong.
As a programmer, it is usually well advised to assume the end-user is an idiot. They will without a doubt find ways to abuse or break stuff in ways you didn't anticipate. HOWEVER, you don't have to teach them how to do EVERYTHING.
If people don't know how to insert custom graphics, or setup exanimation, you are better off pointing just pointing them to a tutorial instead of explaining everything yourself. You are burying the actual important information under tons of (possibly) redundant tutorials on how to do basic stuff.
File list and version history... sure, if you want to but I honestly think you are just wasting your time writing them up for such small scale stuff like this. When I opened the zip, I immediately saw 3 blocks, 1 palette+mask + an ExGFX file for the graphics and whatnot. Nothing that really warrants an in-depth explanation.
Keep your readmes short and to the point. Sometimes less is more. People often get scared off by 200 lines long readmes and don't bother looking for the 10 lines that actually contain the information they need. Sure, if something has a bit of a more complicated setup, go ahead and explain stuff, but don't bother including tutorials on ExGFX and animation when you can just write two lines with links to actual tutorials here on the side.
For example, in this readme, stuff like the information about leaving air between the upside down switch and the ground because you can glitch through or the yoshi block is about everything that is really relevant, no?
While not really a problem, I feel like pointing out that you could also make these a two in one block if you want to, similar to how the exit enabled pipe tiles work from both directions because they always expect the other side to be blocked anyway. You DON'T HAVE TO make it like this, after all, it would then no longer be possible to put the block on tiles that can be accessed from below.
Lastly, the whole "updating" thing in general. Please PLEASE only submit updates if they are really necessary. Not just because they can save 2 bytes and some cycles. It takes me some 10-15 minutes to moderate a simple update like this, because I "simply" compare the new to the old files and see what's changed before testing them in GPS. Plus another 15 for writing an in-depth comment like this.
I (and probably most other moderators too) would really appreciate not having to moderate a whole block pack again and again because it saves 2 bytes or is 10 cycles faster. It usually depends on how much is saved relative to the total code. <Q> 10 byte long code that can be reduced by 2? <A> Sure. <Q> 500 byte code that can be shortened by 2? <A> Do I really have to bother with this?