A simple effect to create in photoshop, take an image the palette of which you like and crop it to just one pixel in a single dimension (so you have a very long and thin or tall and narrow image just one pixel wide or high but many hundreds in the other dimension.
Increase the size of the canvas so there is space to stretch out you line of pixels.
Ctrl-T to transform then stretch your image along it's narrowest side... the results of this can be seen below.