I was so excited to find out from TCRF that there was a fix for the missing tile animation frame, that I fixed the POW block while I was at it. Then I found out that the SMB2 Improvement patch already fixed the animation, and more: http://www.romhacking.net/hacks/2600/
Well, it didn't fix the POW block (the letter "O" is misaligned in one frame), so I'm releasing it to whoever wants it. It's not a super important fix, but like the missing animation frames, it's just something that has bugged me since I was a kid.
Also, "just because", I graphically hacked Mario, Luigi, and Peach to have their eyes match how they look in the menu screens. I almost always play as Toad, so I never noticed how weird the whites of their eyes look, especially when they flicker. The "whites" are still being drawn, you just can't see them anymore, so if someone could ASM hack them out entirely (wink wink, nudge nudge), that might cut down on overall screen flicker a tiny bit.
Anyway, feel free to pick this apart and throw it into other hacks. If you just want the POW fix, I believe the two tiles are at 0x027410 and 0x027430.
Here's the patch file, v0.99: https://www.mediafire.com/?xs650g7ze9zy1a3
Mix it with the Improvement patch linked above for best results.
Edit: Version 1.0 can be found here: http://www.romhacking.net/hacks/3847/