+Digits told me to post this, so here it is. I've discovered that the GF9 magnetic oval bases, seen here, are perfect for bikers and cavalry in 40k. Their bases fit the bikes almost perfectly and fit in with the rest of your 40k army's bases.

Here's how they look on my bikers:


I highly recommend them to anyone who is using cavalry or bikes in their 40k army. They may seem a bit expensive at first, but since they are only going to be used on bikes, you won't need that many. And if you are using an entire army of bikes (like me!) then they are well worth the cost.

They certainly look good. Another idea is:

http://uk.games-workshop.com/spacemarines/basing-bikes/1/

Yeah, those are pretty cool too. The only problem with them is the bases are quite large, so if you have a lot of bikes it becomes tough to move them. However, the article does have some great suggestions for bases and they work well if you only have one squad.