Meatball:
Round note blocks... Does it get much better? I believe there is a ? block ball somewhere, we could make a ball themed level! These look nice and round, good job.
I like the idea of it looks like a nice graphic to add a little something unique to a level, I think it would look nice in a sky level where note blocks are commonly used the most, good job
Though, like the rest have said, the SMB1 is way too dark. And by the way, I think the same of the SMB2 one. You could try to stick with the same palette as the SMB3 and SMW one.