Hi, as it's pixel art, for the right size the whole tileset should be remade in 128x128. Else you can just scale x4 the tiles but you may have dimensions issues in your game.
I'm a bit curious about a pixel art game with 128x128 tiles, do you have already a preview of your game or not ?
Viewing post in Zelda like futuristic - tileset pack comments
Hi Deakcor, I'm not really doing a pixel art per se. I'm experimenting and trying to use the feel of a pixel art game, but with higher res graphics. I'm using blender to make flat coloured low poly characters to attempt to make the game appear modern, but also trying to use pixel art style tiling and sprite sheets to give it a classic feel. That's the goal any way. I've still got a long way to go, but if you like I can send you some links when its a bit more ready.