I made a tileset yesterday in the style of Modern Grass, but what was needed to boost it was a Modern Cave, this cave set is pretty basic, however it works well for a cave level, and can be used with the Modern Grass Set in the same level
Nice tileset! The tileset + background gives you that nostalgic underground level. As what I can see, this fits well with SMB2 type of episodes/levels.
Keep up the nice work!
To me, this looks like a blue recolour of a standard grass tileset.
I think the slopes could use a bit of a more wavy shape where the top part meets the fill. It looks really weird like it is now, because the connecting part is uneven throughout the rest of the tileset.