Some graffiti is, I think, traditional at this point and a good mural can do wonders to humanize it. I have a feeling that patterns are not actually going to improve it though. The problem is often the form rather than what the material looks like. You could paint it to look like a row of thatched cottages but that would to me be even more depressing.
You are also then committed to repainting it regularly or it’s going to quickly look even worse than when you started.