Normal Blue P-Switch Upside down Blue P-Switch Normal Silver P-Switch Upside down Silver P-Switch.
Credit is optimal.
Rejected because you can't activate the P-Switches on the top corners (remember, it's 2020 where MarioCorner is an existing offset for a long time), the silver P-Switch doesn't turn sprites into coins and lack of compatibility without AddmusicK (you have to set the P-Switch music manually when not using AMK).
More minor, you also set the acts like in these blocks when it's completely redunant (unless you make the P-Switch act like 25 so you can't jump off it) and the ground isn't shaking. I also would have wished for more customisability i.e using defines for certain variables (timer, sound effect, music).
Another reason is that we have got the existing but more limited (due to the lack of an upside down P-Switch and graphics but is otherwise more functional and closer to SMW's P-Switches) SMB3 P-Switch Block Set and the customisable but waiting P-Switches (which fixes the aforementioned issues alongside being closer to SMW's P-Switches in general). Both of them also don't disappear in a smoke but actually transform into a flat P-Switch, making the animation more natural.
Lastly (but not completely a rejection reason), it's better to use unused colours (i.e. the second half of the palette) for custom block graphics. I noticed that you only pasted the graphics into an otherwise empty ExGFX file without remapping the colours so the user has to sacrifice two palettes even when it's possible without big loss (e.g. make the P-Switch use colours 5 to 9 or just the second half instead of colours 2 to 7). Speaking of a palette: It's better to include a PAL file (including Palmask) then just figuring the user out on which colours to use.