If you're looking for a shirt pattern that's a step up from striped but a few steps below a Hawaiian shirt, then try polka dots. Not convinced? take a look at Rufus Wainwright.
While it's possible to look good in a Hawaiian shirt, we don't blame you if you'd rather avoid it. Years of negative reinforcement (and overweight tourists) can trick the brain into a bizarre state of style dysmorphia. And you probably wear plain and striped shirts every work day, so wanting something different is understandable.
As Rufus shows, the polka dot shirt is the ideal halfway house. From a distance it looks like a plain shirt, so there's no chance of being mistaken for Tad from Arizona who thinks his Hawaiian shirt hides his expanding waistline. And the fact that it isn't actually a plain shirt means you won't feel like you're going to work when you've got it on.
The key things to look out for is to stick to a dark shirt colour with light polka dots. If you wear it the other way around you'll look like a chickenpox sufferer, which is never desirable. A good option is this shirt by Barbour (£80, ASOS) which avoids the pox look and looks just as good on its own as it would under a jumper.
Paul Smith polka dot shirt (£120, Julesb)
Oliver Spencer polka dot shirt (£120, mr-porter)