Tonight I thought I would end up with a dud, because I left it till the last minute. But I was inspired by my bathroom floor. Unfortunately our bathroom floor is not this white, but I used the "Enhance color" button on Picture Manager. When you click this button, the cursor becomes little cross-hairs, which you then place over any part of the picture that is truly white (or that you wish was truly white). When you click, it adjusts the colors accordingly. In this case it makes the photo look black and white, but if you look carefully you can see some colored bits of dust.
I really like this particular picture, but I must admit that one of the reasons I chose it was because it was the one that made our bathroom floor look the cleanest.