There are three main issues from memory (I'm not well-versed in RPG Maker):
- These aren't in the format that RPG Maker VX Ace accepts, so you'll need to shift things around so they fit how VX Ace wants them.
- These are 16x16 pixel tiles. RPG Maker VX Ace uses 32x32 pixel tiles I think. You could double the size of the tiles to make them fit, but they'll have bigger pixels than everything else assuming they also haven't been doubled.
- I believe the auto-tiling that RPG Maker uses is not that same format that I've used here, so you will have to do some editing if you want to use the auto-tiling terrains in RPG Maker.