With update 24.00, Epic added these two itemshop backgrounds with the tags "SnowfallDot" and "WaveTexture."
At the moment it's not known what they are for, but it's possible that they could be used for a future collaboration.
#Blender's WaveTexture node was much ezer to port to glsl, but the results are thicker lines with the same settings. It shares some parts with NoiseTexture, so all the hard bits was already done. Only change needed to do was replace str /w enums, cause #glsl doesn't do strings.