I dont know if by "white background" you mean the "interface on song selection screen", the "background in the gameplay screen" or the "inputoverlay background".
Interface on SSS: not neccessarily hard to make, you can just make some areas completely white, but might have to make the selection-mode images another color than white.
Gameplay background:
beatmapsets/752832#osu/1584908 this map has made a way to make the whole background white without obscuring any other part of gameplay/your skin, any other method obscures some part of gameplay.
inputoverlay background: this has been a choice made by peppy ages ago, you cant change it, except by making the color multiply with yellow to make the pressed color different.
If there is anything else you meant, feel free to write back.