No cake for spunky
There is really two issues here. First which of the many residuals that can be generated to look (this is from SAS). Second, I am trying to detect non-linearity (I tested for multicollinearity and there is none, with 5,000 plus points I don't care about heteroskedasticity or normality). But I can never tell with blobs of data like this whether the data is non-linear. None of the books I have ever seen show residuals like this in discussing the data.