What you need to do is resize the default textures. Use...well..in photoshop it is called nearest neighbor when you resize to avoid getting blurry lines. You could also find a 32x template. I know there is a thread floating around that has templates for different resolutions.
Also, you could visit my link hub. I have created a tutorial thread with a link to some templates
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"Look, I don't care if your 8 or 20. If you can't take criticism or opinions, then get off the internet." -Stronghold257
Yeah, once the canvas is resized as I specified in my previous post, you gotta resize the actual picture, which is still too small. You select the textures with the rectangle selection tool, then you resize them to fit the new, larger canvas (using the blue arrow tool). You will have a drop-down menu near the top left corner of the screen which will say:
You have to select the "Pixelated" option in that drop-down menu to avoid getting everything blurry.