A book cover is just an image. That's all it is. You can take a photo, and use that. You can get a copyright free image off the intrent and use that. You can use an image editor like the GIMP to change it how you want, then use the resultant image
Tags are for the search engine, nothing to do with book cover
Nightmare412 wait, it's impossible to have two cats as your book cover unless you intentionally set it as that...are you sure you're looking at the right thing?
And no, any image you choose for you book cover needs to first be saved on your hard drive. And don't even think about taking just any image you find from the internet, that's illegal