Images are a nuisance. They can be beautiful when you design them but upload them to an ebook asn the magic can be lost instantly. This is my little guide, mostly for my own benefit so I don’t have to search the KDP website for minor details such as optimum sizes etc.
Covers are difficult. You might want to make them so they stand out on the Kindle store. If you have a non-fiction book sometimes it is nice to have a square cover, but otherwise I feel filling a Kindle screen would be better in which case a rectangle fits the need.
Another thing to consider is that when designing your Kindle Cover, have a look at a thumbnail before you make your final decision. This is what customers will see when they browse.
KDP advise the PNG format in one section of their help pages, bitmaps are too big and gifs too limited, which I agree with in my limited experience. Although in a different part of the website they recommend using jpegs. Usefully they also mention that the content is shown in 16 shades of grey on some Kindles.
So looking quickly through the nightmare of help pages, still trying to find the right size to create the images in the first place, my husband walks in suggesting I look at jailbroken Kindle pages. He was right. The optimum size is 600px by 800px. Genius.
Right off to make some images now…