Thanks! It depends on the texture--sometimes I use photos I take or find on texture website and modify/shrink them, other times I just do it by hand i.e. pixel art. I also use a program to quantize the color to mimic PS1's limited color palette: https://www.softpedia.com/get/Multimedia/Graphic/Graphic-Others/Color-quantizer....
Hope this helps and good luck with your project!