Cover Image Update
Worthy of another mention: We can now accommodate larger, higher-quality cover images for Kindle titles! Accordingly we have updated our guidelines for creating a catalog/cover image. Our new guidelines for cover images require that an image be at least 1,000 pixels on the longest side, though we recommend 2,500 pixels on the longest side to ensure better quality, and an ideal height/width ratio of 1.6. To confirm whether your cover image meets these requirements, right-click the image file and select "Properties."
I'm not entirely convinced that bigger image files are in the vested interests of the readers because Kindles, like everything else connected to the internet, have to deal with the so-called "bottleneck" effect of downloading and displaying information over a wireless or 3G connection. Bigger image files, while looking nicer, open the opportunity for slower-loading files.
As a former web graphics designer, who learned from Day One of the web that optimizing images for web use will make or break a network-based presentation, I'm worried. My concern is for the customers, the readers, falling prey to the ignorance of Indie Authors who create their own image files. Most of them won't have a clue that a way to reduce file size without losing image quality even exists, let alone how to do it.
So here's a follow-on tip. If you want to use a larger, higher-resolution image for your book cover, please consider hiring a professional web graphics designer to create your cover for you. The size of your cover image file not only adversely affects your file-loading time, but the larger the image, the smaller your text sample will be. That's right, a bigger image means your readers get less of your book when they download the free sample--maybe just a page or two if your cover image file's huge enough!
Plus, a professional designer will do a professional job laying your cover or even conceptualizing the imagery for you in an artistic way. Oh and don't forget, professional designers usually have a toolbox of great fonts on hand. Your book cover will benefit in a myriad of ways. Just find a barter if you can't cough up the cash. There's always a way to "pay" for what you need to get your book done "right."