Can I send the picture I want to be used on my book cover?

Yes, as long as it's high resolution and you own the usage rights. Please keep in mind that although Google is full of wonderful images, most of them cannot be used on commercial products, such as book covers. Just because the image doesn't have the © symbol somewhere on it, doesn't mean it's free to use. The opposite is in fact true. Every image, photo or illustration on the internet are bound by copyrights, unless openly stated otherwise. Either you will need a written permission from the artist to use the image or buy it online from a stock photo site.   As for your own drawings, illustrations or photos, yes they can be used. But unless they are professionally made, we would recommend you not to use them. Remember, a book cover is a commercial product so should look professional and catchy more than anything else.