That logo can be used on the back cover of your paperback, CreateSpace allow for this on their free templates.
I'd like to say that I did extensive research into creating a logo, but in all honesty I googled 'create free logo'. That search found Logo Garden (click on the name to find their website). You can create a perfectly adequate logo for free. However, if you want it to be of a good printable quality, you need to purchase a hi-res version. Because I shall use it for other publications, I decided to pay the £8. I can edit the logo and the clever folk at Logo Garden will also re-size it for free. That's something I needed – it had to fit into the set box of the template. But if you design your logo to fit the box, you might not need their help.
As I shall re-use the logo, and it's not essential to the process, I'm not including it as a 'cost' – it's more of a long-term investment!
If you're wondering why I fiddled with logos after I'd finished the book and ordered the proof copy, it's simple. You can edit your book every day – the content and cover. So whilst I waited for the proof copy, I continued to polish (not play!).