Maybe change the flowers at the top of the screen to backpacks? Looking forward to seeing how this turns out, it’s a great idea 
I had the idea of changing them into the pencils from SFC, the carrots from Shun, or some other background object from the games.
I'm using yychr and I'm having a good time of it. the tricky bits are that the dig dug dude sprites are actually five colors, not four, as there's a hidden collision bounding area, with them getting a little tricky with some layering to get the red tools, but it's not really a big deal to ignore that and just make the sprites four color for a first pass. I'm having fun learning about all this stuff ^_^
I notice that there's also some "getting squished" sprites in there as well, for when a boulder falls on you. I was just gonna improvise but idk if you wanteed to make some "official" ones for our spriteset or not :3
yychr? Okay, I'll see what I can do.
...And whoa, I totally missed that sprite. Well, here's Kawase getting squished.
And the non-upscaled image. (Is there a better way to say it than "non-upscaled"? Unupscaled isn't a word, right? Non-upscaled doesn't roll off the tongue very nicely.) I also put the other sprites behind a colored background - that way you can differentiate between "part of the sprite" black and "part of the background" black, in case that's needed. They'll look a little weird not being on black backgrounds, but hey, function over form. I'll do that for future sprites too.
Also, Combi your sprites are amazing! ^_^
You're amazing!