Luckily, the Terraria forums has the solution for us! Multiple, actually. We need to convert them into something our PC can recognize. Those XNB files are the sprites we want to modify, but simply opening them in an image editing program isn't gonna work. If you've ever peeked into Terraria's assets folders, you've probably noticed these 'XNB' filetypes.
If you wanna create your own texture packs, the first thing you need to do is find the textures you want to modify. actually, why would you do that? It's 10 bucks dude, just buy it. If you're using GOG, this guide might be harder to follow. It only makes sense, seeing as you're looking at a Steam guide and all.
Before we go further, I should clarify that this guide will operate under the assumption that you're using the Steam version of the game.
