When you say "textures"... are we talking about a 3D game or a 2D game here? "texture" is a term used in 3D graphics, but I'll assume this is about 2D for now as that's what GameMaker excels at.
It really depends on how your game is set up. Figure out the native resolution your game will be using and create the graphics accordingly.
Ideally, you want your native resolution to either be exactly the same as, or an even divider of, your target resolution. Your target resolution depends on what kinds of devices you plan for the game to be played on and the common resolutions those devices have right now (or will have at the point your game is planned to be released - but this may require psychic abilities and/or a bit of foresight and market prediction).
Not all displays use the same aspect ratio, though, so factor that in when deciding. You can adapt your game's camera and view dynamically according to the aspect ratio of the player's display if it doesn't exactly match your game's base aspect ratio, so that your game in turn matches the display's aspect ratio without causing distortion. Distortion is what happens when the pixels you're rendering don't translate evenly to pixels on the screen - because there are no "half pixels", the result can't be scaled and displayed evenly.
Once you know the target resolution, you can figure out the native resolution. In order to not introduce distortion during upscaling, this needs to be an even divider of the target resolution. For example, if your target resolution is 1080p (1920x1080), your potential native resolutions are 1920x1080, 960x540 (divided by 2), 640x360 (divided by 3), 480x270 (divided by 4)... and so on. There's no formula for this, you have to check and see what suits your game.
The native resolution will provide you with a frame of reference of how big your graphics will look in the game, relative to the total size of the display. At this point, you're done for the most part.
There's one more thing to keep in mind, though, and that's scaling. If there's any kind of zooming or scaling going on in your game, you have to take this into consideration if you want your graphics to retain a crisp look without individual pixels being discernible. (If you want this to be the case, this part is void.)
If the maximum amount of scaling in your game is 200%, that means you will need 200% more pixels to accomodate for the scaling, and need to downscale drawn graphics accordingly (the graphic is now twice as large, so you have to draw it at half the size). When zoomed in, the zoom factor and the downscaling factor cancel each other out, leading to it being drawn at full scale when fully zoomed in.
More importantly than making sure everything looks good at max scale, make sure that everything looks good at 100% scale. Design graphics to look good by default, not only when scaled - small details may easily get lost when you design them with the fully scaled resolution in mind, rather than the default scale.