I am a sucker for fun buttons. I have a disturbingly large button stash, and I have even been known to design entire cardigans just to feature certain buttons (and I have several more in mind as I type this!).
You may not know this, but we have a small but eclectic button collection here at the store. In the past, only a handful of them have been featured on the website - but I am working to add all of them all now. Keep an eye on the button section of our website - I hope to get everything added this weekend! :)
The photos can be a little deceiving for size, so I am doing my best to include measurements. I usually suggest that you choose your buttons after knitting your garment, because sometimes you fall in love with a button, and then it won't fit through your buttonhole. So sad! That said, there are many different ways to create a buttonhole in knitwear - while each of them have their own strengths and weaknesses, there's no reason why you can't swap to a different buttonhole to accommodate those beloved buttons.
You can read about different buttonhole methods - and how to work them - here. My favourite is the two-stitch eyelet buttonhole that is described at the bottom of the page. They tend to require smaller buttons, but unless you're making a coat with large buttons, its not really a problem. Also, knitted buttonholes can stretch out over time - start small, and then it won't be a problem if you have to switch to bigger buttons a few years down the road. :)