The site's background is fine. It's tacky.It's cool. It's something different. I know some people don't like smoking, but it's just a picture that's meant to be funny. If you didn't already notice, there is a "no smoking" sign on the top left corner of the site. The fact that the cute redhead is breaking the rules by smoking kind of defnes Newgrounds in a way. It's a site that's meant to question the status quo and be a little bit different. Newgrounds is userbased site that lets users decide and vote for what they want to keep on the site. Sometimes you get the haters that just rate every submission with a "0", but they're usually just trolls who don't stay on the site long enough to get a high batting average so it doesn't make much of a difference.
Who knows, maybe Newgrounds will make a poll that lets the Newgrounders decide on if they want to keep the "smoking" background. But hey,Tom and the rest of the group might eventually change the background, but for now it's fine. It's got the orange colour scheme of the old site and the other site pages are colour coded accordingly. And besides, they underwent extreme site maintenence just days ago to bring you that "smoking" background along with the rest of the nifty little changes.
Lastly, if you don't like smoking, maybe you should start a "Non Smokers" club. That might help you agonize over these site chages better.