Hey this is Pays164, and now I'm going to give you some tips in graffiti background. Sometimes it doesn't have to be too complex if you're running out of wall space, but picking good colors to fade around your piece so that you can silhouette images such as city building, subway cars and whatnot.
First are purple, and then I'm going to lead to some other colors. So, again this is just a simple effect and including a background to your graffiti mural. I went through with some purples, to reds, to orange, to yellow creating a consistent fade kind of giving it a sunset effect. Now I'm going to come back with my black, again a darker color to go with the contrast of the back of the wall is silhouetting, shadows, city buildings.
I'll go through and build little groupings of buildings throughout the background over the fade edges created. Really cool little city background you all. If you have more space really the background can be anything. Mountains, characters, any kind of scheme you want to create. More space might also allow you to do thing much bigger. Creating more color inside your background as a fill.